Definition of terms

Terms related to administrative divisions

A subdivision of the barangay, especially used in many rural areas in the Philippines. Purok often serves as a unit for delivering services and administration within a barangay. Source: Community-Based Monitoring System - Philippine Statistics Authority
A territorial enclave that forms part of a barangay, the location of which may be distant from the center of the barangay itself. Source: Community-Based Monitoring System - Philippine Statistics Authority
A sitio is not an administrative unit and its characteristics and geographical boundaries are not officially defined by the government. It is a geographical area that is part of a barangay and usually distant from the center of the barangay economic and social activities. Source: National Economic and Development Authority Region IX

Terms related to demography

Age dependency ratio
The ratio of persons in "dependent" ages (generally under age 15 and over age 64) to those in "economically productive" ages (15 to 64 years) in the population. It is sometimes divided into the old-age dependency (the ratio of people aged 65 and older to those aged 15 to 64 years), and the child dependency (ratio of people under 15 to those aged 15 to 64 years). Source: Philippine Statistics Authority
Household Population
The population enumerated in private households during a census. Source: Philippine Statistics Authority [compare with Institutional population]
Institutional Population
The population enumerated during a census living in large institutions, such as national prisons and penal colonies, provincial and large city jails, tuberculosis sanitaria, mental hospitals, leprosaria, military, mining and logging camps, etc. The cut-off is more than 6-months duration. Source: Philippine Statistics Authority [compare with Household population]
The total number of individuals in a territory at a specified time. It covers both nationals and aliens, native and foreign born persons, internees, refugees and any other group physically present within the borders of a country at a specified time. Source: Philippine Statistics Authority
Median age
The age that divides a population into two numerically equal groups, that is, half of the population are younger than this age, and the other half are older. Source: Philippine Statistics Authority
Population growth rate
The rate at which the population increases within a given time or period. Applies/refers to the calculated growth rates between each census.

Terms related to distance

Great-circle distance
The shortest distance between two points along the surface of a sphere or ellipsoid. Applies/refers to the shortest distance between two cities or towns (using the city/municipal center coordinates as points).

Terms related to landforms

a ring-shaped coral reef which has closely spaced islands on it encircling a lagoon
an elevation, typically located on a shelf, over which the depth of water is relatively shallow but sufficient for most surface navigation
a shallow ridge or mound of coarse unconsolidated material in a stream channel, at the mouth of a stream, estuary, or lagoon and in the wave-break zone along coasts
a shore zone of coarse unconsolidated sediment that extends from the low-water line to the highest reach of storm waves
a small, isolated, usually flat-topped hill with steep sides
a depression measuring kilometers across formed by the collapse of a volcanic mountain
a deep, narrow valley with steep sides cutting into a plateau or mountainous area
a land area, more prominent than a point, projecting into the sea and marking a notable change in coastal direction
an underground passageway or chamber or cavity on the side of a cliff
a high, steep to perpendicular slope overlooking a waterbody or lower area
a generally circular saucer or bowl-shaped depression caused by volcanic or meteorite explosive action
a flat plain formed by alluvial deposits at the mouth of a stream
a large area with little or no vegetation due to extreme environmental conditions
a long line of cliffs or steep slopes separating level surfaces above and below
a low place in a ridge, not used for transportation
a short, narrow, steep-sided section of a stream valley
a high projection of land extending into a large body of water beyond the line of the coast
a rounded elevation of limited extent rising above the surrounding land with local relief of less than 300 meters
a tract of land, smaller than a continent, surrounded by water at high water/high tide
a narrow strip of land connecting two larger land masses and bordered by water
a flat-topped, isolated elevation with steep slopes on all sides, less extensive than a plateau
an elevation standing high above the surrounding area with small summit area, steep slopes and local relief of 300 meters or more
a mountain range or a group of mountains or high ridges
a break in a mountain range or other high obstruction, used for transportation from one side to the other
a pointed elevation atop a mountain, ridge, or other hypsographic feature
an elongate area of land projecting into a body of water and nearly surrounded by water
an extensive area of comparatively level to gently undulating land, lacking surface irregularities, and usually adjacent to a higher area
an elevated plain with steep slopes on one or more sides, and often with incised streams
a tapering piece of land projecting into a body of water, less prominent than a cape
a broad elevation that rises gently, and generally smoothly, from the sea floor
a broad, open pass crossing a ridge or between hills or mountains
a narrow zone bordering a waterbody which covers and uncovers at high and low water, respectively
an elongated depression usually traversed by a stream
a conical elevation composed of volcanic materials with a crater at the top

Terms related to waterbodies

a coastal indentation between two capes or headlands, larger than a cove but smaller than a gulf
the deepest part of a stream, bay, lagoon, or strait, through which the main current flows
a zone of variable width straddling the shoreline
a place where two or more streams or intermittent streams flow together
a small coastal indentation, smaller than a bay
Crater Lake
a lake in a crater or caldera
a branch which flows away from the main stream, as in a delta or irrigation canal
a funnel-shaped stream mouth or embayment where fresh water mixes with sea water under tidal influences
a type of hot spring with intermittent eruptions of jets of hot water and steam
a large recess in the coastline, larger than a bay
a haven or space of deep water so sheltered by the adjacent land as to afford a safe anchorage for ships
the source and upper part of a stream, including the upper drainage basin
a narrow waterway extending into the land, or connecting a bay or lagoon with a larger body of water
a shallow coastal waterbody, completely or partly separated from a larger body of water by a barrier island, coral reef or other depositional feature
a large inland body of standing water
a wetland dominated by grass-like vegetation
one of the major divisions of the vast expanse of salt water covering part of the earth
a small standing waterbody
a surface-navigation hazard composed of consolidated material
Salt Lake
an inland body of salt water with no outlet
a large body of salt water more or less confined by continuous land or chains of islands forming a subdivision of an ocean
a surface-navigation hazard composed of unconsolidated material
a long arm of the sea forming a channel between the mainland and an island or islands; or connecting two larger bodies of water
a relatively narrow waterway, usually narrower and less extensive than a sound, connecting two larger bodies of water
a body of running water moving to a lower level in a channel on land
Stream Mouth
a place where a stream discharges into a lagoon, lake, or the sea
a wetland dominated by tree vegetation
a long, narrow, characteristically very deep and asymmetrical depression of the sea floor, with relatively steep sides
a long depression of the sea floor characteristically flat bottomed and steep sided, and normally shallower than a trench
a perpendicular or very steep descent of the water of a stream

Terms related to Maritime Zones of the Philippines

Archipelagic Baselines
Baselines specifically defined and described in Section I of Republic Act No. 9522, entitled "An Act to amend certain provisions of Republic Act No. 3046, as amended by Republic Act No. 5446, to define the archipelagic baselines of the Philippines, and for other purposes".
Archipelagic Waters
The waters on the landward side of the archipelagic baseline.
Contiguous Zone
The waters beyond and adjacent to the territorial sea and up to the extent of twenty-four (24) nautical miles from the baselines or from the low-water line, as the case may be.
Continental Shelf
Comprises the seabed and subsoil of the submarine areas that extend beyond its territorial sea throughout the natural prolongation of its land territory to the outer edge of the continental margin, or to a distance of two-hundred (200) nautical miles from the baselines from which the breadth of the territorial sea is measured, where the outer edge of the continental margin does not extend up to that distance.
Exclusive Economic Zone (EEZ) of the Philippines
The waters beyond and adjacent to its territorial sea and up to the extent of two-hundred (200) nautical miles from the baselines or from the low-water line, as the case may be.
Internal Waters
Refer to (a) the waters on the landward side of the archipelagic baselines not forming part of the Archipelagic Waters delimited in accordance with Article 50 of the 1982 United Nations Convention on the Law of the Sea (UNCLOS); and/or (b) waters on the landward side of the baseline of the territorial sea of territories outside of the archipelagic baselines.
Territorial Sea
Shall be the belt of sea measured twelve (12) nautical miles from the baselines, or from the low-water line, as the case may be.


  • 16th Congress of the Republic of the Philippines, First Regular Session: Senate Bill No. 93 entitled "An Act to define the Maritime Zones of the Republic of the Philippines".
  • 18th Congress, First Regular Session: House Bill No. 808 entitled "An Act defining the Maritime Zones of the Philippines".
  • Republic Act No. 9522 entitled "An Act to amend certain provisions of Republic Act No. 3046, as amended by Republic Act No. 5446, to define the archipelagic baselines of the Philippines, and for other purposes".

Terms related to rivers

The place where a river begins is called its source. River sources are also called headwaters. Source: National Geographic Society. "Source." National Geographic, 9 Oct. 2012,
River basin
A river drainage basin is an area drained by a river and all of its tributaries. A river basin is made up of many different watersheds. Source: National Geographic Society. "Basin." National Geographic, 9 Oct. 2012,
River mouth
The place where a river enters a lake, larger river, or the ocean. Source: National Geographic Society. "Mouth." National Geographic, 9 Oct. 2012,
A freshwater stream that feeds into a larger stream, river or other body of water. Source: National Geographic Society. "Tributary." National Geographic, 9 Oct. 2012,
A watershed is an entire river system — an area drained by a river and its tributaries. It is sometimes called a drainage basin. Source: National Geographic Society. "Watershed." National Geographic, 9 Oct. 2012,

Terms related to caves, ecotourism, and Protected Areas

any naturally occurring void, cavity, recess or system of interconnected passages beneath the surface of the earth or within a cliff or ledge and which is large enough to permit an individual to enter, whether or not the entrance, located either on private or public land, is naturally formed or man-made. It shall include any natural pit, sinkhole, or other feature which is an extension of the entrance. The term also includes cave resources therein but not any vug, mine tunnel, aqueduct or other man-made excavation.
Cave resources
includes any material or substance occurring naturally in caves, such as animal life, plant life, including paleontological and archaeological deposits, cultural artifacts, or products of human activities, sediments, minerals, speleogens and speleothems.
relief features on the walls, ceilings and floors of any cave or lava tube which are part of the surrounding bedrock, including but not limited to anastomoses, scallops, meander niches, petromorphs and rock pendants in solution caves and similar features unique to volcanic caves.
any natural mineral formation or deposit occurring in a cave or lava tube, including but not limited to any stalactite, stalagmite, helictite, cave flower, flowstone, concretion, drapery, rimstone or formation of clay or mud.
Protected area
identified portions of land and/or water set aside by reason of their unique physical and biological diversity and protected against destructive human exploitation.

Categories of protected areas:

  1. Strict nature reserve – an area possessing some outstanding ecosystem features, and species of flora and fauna of national scientific importance that should be maintained to protect and to preserve nature in its undisturbed state to preserve ecologically representative examples of the natural environment to ensure their availability for scientific study, environmental monitoring, education, and for the maintenance of genetic resources in a dynamic and evolutionary state.
  2. Natural park – a relatively large area not materially altered by human activity where extractive resources uses are not allowed and is maintained to protect outstanding natural and scenic areas of national or international significance for scientific, educational, and recreational use.
  3. Natural monument – a relatively small area focused on the protection of small features to protect or preserve nationally significant natural features on account of their special interest or unique characteristics
  4. Wildlife Sanctuary – an area which assures the natural conditions necessary to protect nationally significant species, groups of species, biotic communities or physical features of the environment which may require specific human manipulations for their perpetuation.
  5. Protected landscapes and/or seascapes – areas of national significance which are characterized by the harmonious interaction of man and land and water while providing opportunities for public enjoyment through recreation, tourism, and other economic activities
  6. Resource reserve – an extensive, relatively isolated, and uninhabited area which is difficult to access and is designated to protect the natural resources of the area for future use and prevent or contain development activities that could affect the resources, pending the establishment of sustainable resource utilization goals which are based upon appropriate information and planning
  7. Natural biotic area – an area set aside to allow the way of life of societies living in harmony with the environment to adapt to modern technology at their pace; and
  8. Other categories established by law conventions or international agreements which the Philippine Government is a signatory.
Endemic species
species or subspecies of flora and fauna which are naturally occurring and found within specific areas in the country
Exotic species
species or subspecies of flora and fauna which do not naturally occur within the protected area at present or in historical time
Protected species
plants or animals declared protected under Philippine laws, rules, and regulations. These shall include all species listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora and all its Annexes, the Convention on the Conservation of Migratory Species (CMS), those specified under the red-list categories of the International Union for Conservation of Nature and Natural Resources (IUCN), or any plant or animal which the Department of Environment and Natural Resources (DENR), PAMB or any government agency may deem necessary for conservation and preservation in the protected area
Threatened species
species or subspecies considered critically endangered, vulnerable, or other accepted categories of wildlife whose population is at risk of extinction
wild forms and varieties of flora and fauna, in all developmental stages, including those which are in captivity or are being bred, fed, or propagated
gathering, collecting, or possessing products or natural resources from the protected area by any individual person, corporation or entity whether local or foreign; in the case of marine protected areas, operating any foreign fishing vessels by any person, corporation, or entity without a permit
a wide variety of inland habitats such as marshes, peatlands, floodplains, rivers and lakes, and coastal areas such as saltmarshes, mangroves, intertidal mudflats and seagrass beds, and also coral reefs and other marine areas no deeper than six (6) meters at low tide, as well as human-made wetlands such as dams, reservoirs, rice paddies and wastewater treatment ponds and lagoons
a low-impact, environmentally-sound and community-participatory tourism activity in a given natural environment that enhances the conservation of biophysical and cultural diversity, promotes environmental understanding and education, and yields socioeconomic benefit to the concerned community

Ecotourism activities must have all the following attributes:

  1. environmentally-sound and low-impact development;
  2. with educational value;
  3. have community acceptance and participation; and
  4. provide social and economic benefits to the concerned community thru livelihood undertakings.


  • Republic Act No. 9072 or "National Caves and Cave Resources Management and Protection Act" dated 24 July 2002.
  • Republic Act No. 11038, otherwise known as the "Expanded National Integrated Protected Areas System Act of 2018".
  • Republic Act No. 7586, known as the "National Integrated Protected Areas System Act of 1992".
  • Joint DENR-DOT Memorandum Circular No. 98-02 dated 29 June 1998: Guidelines for Ecotourism for Development of the Philippines.

Terms related to roads

Primary Road
National Road classification, a road that connects major cities with population of at least 100,000. Source: Department of Public Works and Highways
Secondary Road
National Road classification, a road which complements the national primary roads to provide access to main population and production centers of the country. Source: Department of Public Works and Highways
Tertiary Road
National Road classification, an existing road under the DPWH which performs a local function. Source: Department of Public Works and Highways

Terms related to volcanoes

Erupted within historical times (within the last 600 years). Source: Philippine Institute of Volcanology and Seismology
Potentially active
Morphologically young-looking but with no historical or analytical records of eruptions. Source: Philippine Institute of Volcanology and Seismology
No recorded eruptions; physical form has been intensively weathered and eroded, bearing deep and long gullies. Source: Philippine Institute of Volcanology and Seismology

Terms related to Disasters in the Philippines

Dangerous storms that include lightning and can bring powerful winds over 80 kph (50 mph), create hail, and cause flashfloods and tornadoes. Source: "Thunderstorms and Lightning." Official website of US Homeland Security (
A seasonal shift in the prevailing wind direction, that usually brings with it a different kind of weather. It almost always refers to the Asian monsoon, a large region extending from India to Southeast Asia where monsoon conditions prevail. Source: "What is a monsoon?" Weather Questions,, 2 Nov. 2012,
In the Philippines, the monsoon consists of the Northeast Monsoon, called Amihan, and the Southwest Monsoon, or Habagat. The Northeast Monsoon brings cool and dry air originating from Siberia, Mongolia, and northern China at a time when these countries are going through winter. Such wind system causes cloud formation and rainfall over the eastern sections of the country from November to February each year.
The Southwest Monsoon or Habagat consists of seasonal winds blowing from the southwest direction which cause extensive cloud formation and rainfall over the western sections of the country. Habagat occurs during the months of June to October each year. Source: Ganal, Jr., Romeo R. "Effects of Monsoons in the Philippines." Official website of DOST-PAGASA (
Typhoon/hurricane/tropical cyclone
The only difference between a hurricane and a typhoon is the location where the storm occurs. Hurricanes and typhoon are the same weather phenomenon: tropical cyclones. A tropical cyclone is a generic term used by meteorologists to describe a rotating, organized system of clouds and thunderstorms that originate over tropical or subtropical waters and has closed, low-level circulation.
In the North Atlantic Ocean, central North Pacific, and eastern North Pacific, the term hurricane is used. The same type of disturbance in the Northwest Pacific is called a typhoon. Meanwhile, in the south Pacific and Indian Ocean, the generic term tropical cyclone is used, regardless of the strength of the wind associated with the weather system.
The ingredients for tropical cyclones include pre-existing weather disturbance, warm tropical oceans, moisture, and relatively light winds. If the right conditions persist long enough, they can combine to produce the violent winds, large waves, torrential rains, and floods we associate with this phenomenon. Source: "What is the difference between a hurricane and a typhoon?" Official website of the US Department of Commerce - National Oceanic and Atmospheric Administration (NOAA). National Ocean Service -

A tropical cyclone is classified according to its strength and grouped according to the maximum sustained winds near the center:

  1. Tropical Depression (TD) – 61 kph or less
  2. Tropical Storm (TS) – 62 to 88 kph
  3. Severe Tropical Storm (STS) – 89 to 117 kph
  4. Typhoon (Ty) – 118 to 220 kph
  5. Super Typhoon (ST) – more than 220 kph
Source: DOST-PAGASA website
Storm surge
The rising of the sea level associated with the passing of a tropical storm or typhoon. This is due to the push of strong winds in the water surface, the piling up of big waves, pressure setup and astronomical tide moving towards the shore. In other words, the stronger the winds or the larger the storm, the higher the surge. Source: "What Is Storm Surge?" Department of Health Website, Accessed 24 July 2019.
A storm surge brings widespread floods which can extend to kilometers from the seashore depending on the shape and height of the wave. Along with strong waves and forceful winds, a storm surge can destroy and wash away anything in its path.
The rise of water in rivers, creeks, lakes, and other bodies of water which overflows to low-lying areas. This could result to a destruction of property and loss of life. Source: Official Gazette of the Republic of the Philippines, Accessed 24 July 2019.
The mass movement of rock, soil, and debris down a slope due to gravity. It occurs when the driving force is greater than the resisting force. The following can trigger a landslide: intense rainfall, weathering of rocks, ground vibrations created during earthquakes, and volcanic activity. Source: "Introduction to Landslide." PHIVOLCS, Accessed 24 July 2019.
Pacific Ring of Fire
A band of volcanoes and fault lines circling the edges of the Pacific Ocean. It is also called the Circum-Pacific seismic belt; it is shaped like a horseshoe and is 40,000 kilometers (25,000 miles) long. It runs from Chile northwards along the South American coast through Central America, Mexico, the west coast of the United States, and the southern part of Alaska, through the Aleutian Islands to Japan, the Philippines, and Indonesia, before curving back towards New Guinea, the southwest Pacific islands, and New Zealand. The area's seismic activity results from collisions between tectonic plates of the world's some 1,500 active volcanoes, almost 90% of which are in the Ring of Fire. Seventy-five percent of the Earth's active and dormant volcanoes are located in the area. Ninety percent of the world's earthquakes and 81 percent of the world's largest earthquakes occur within it. Source: "What is the Ring of Fire?", North East Arizona Energy Services Company, Accessed 24 July 2019.
An intense shaking of the Earth's surface. The shaking is caused by movements in Earth's outermost layer. An earthquake is the sudden movement of Earth's crust at a fault line. The location where an earthquake begins is called the epicenter. An earthquake's most intense shaking is often felt near the epicenter. The energy from an earthquake travels through Earth in vibrations called seismic waves. Scientists can measure these seismic waves on instruments called seismometer. A seismometer detects seismic waves below the instrument and records them as series of zig-zags. Source: "What Is an Earthquake?" NASA Space Place – NASA Science for Kids, 17 July 2019,
An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel. Source: "Earthquake Glossary." USGS Earthquake Hazards Program, Accessed 24 July 2019.
Magnitude and Intensity
Magnitude and intensity measure different characteristics of earthquakes. Magnitude measures the energy released at the source of the earthquake. Magnitude is determined from measurements on seismographs. Intensity measures the strength of shaking produced by the earthquake at a certain location. Source:
Seismograph and Seismometer
Seismographs are instruments used to record the motion of the ground during an earthquake. They are installed on the ground throughout the world and operated as part of a seismograph network.
A seismometer is the internal part of the seismograph which may be a pendulum or a mass mounted a spring; however, it is often used synonymously with "seismograph."
A seismogram is the recording of a ground shaking at the specific location of the instrument. Source: "Seismometers, Seismographs, Seismograms - What's the Difference? How Do They Work?" United States Geological Survey, 2012,
A series of sea waves commonly generated by under-the-sea earthquakes and whose heights could be greater than 5 meters. It is erroneously called tidal waves and sometimes mistakenly associated with storm surges. tsunamis can occur when the earthquake is shallow-seated and strong enough to displace parts of the seabed and disturb the mass of water over it.
Tsunamis can also be produced by other natural phenomena aside from an undersea earthquake, and these include underwater landslides, volcanic eruptions, and very rarely by large meteorite impacts in the ocean.

There are 2 types of tsunami generation.

  1. Local tsunamis – are confined to coasts within a hundred kilometers of the source, usually an earthquake and a landslide or a pyroclastic flow. They can reach the shoreline within 2 to 5 minutes. The coastal areas in the Philippines especially those facing the Pacific Ocean, South China Sea, Sulu Sea, and Celebes Sea can be affected by tsunamis that may be generated by local earthquakes.
  2. Far field or distant tsunamis – can travel from 1 to 24 hours before reaching the coast of the nearby countries. These tsunamis mainly come from the countries bordering the Pacific Ocean like Chile, Alaska in USA, and Japan. The Pacific Tsunami Warning Center (PTWC) and Northwest Pacific Tsunami Warning Advisory Center (NWPTAC) are the responsible agencies that closely monitor Pacific-wide tsunami events and send tsunami warning to the countries around the Pacific Ocean.

Natural Signs of an Approaching Tsunami

  1. A felt earthquake
  2. Unusual sea level change
  3. Rumbling sound of approaching waves
Source: "Introduction to Tsunami." PHIVOLCS, Accessed 24 July 2019.
Refers to those earthquakes commonly along major subduction zone plate boundaries such as those bordering the Pacific Ocean that can generate tsunamis. Source: "Earthquake Glossary." USGS Earthquake Hazards Program, Accessed 24 July 2019.
GO BAG (Emergency Preparedness Bag)
When there is an impending danger, we need to leave our homes and evacuate to safer areas. To prepare for these emergencies, we should have a ready GO BAG that we can bring along immediately.

Contents of a GO BAG

  • Important documents in waterproof container
  • Flashlight, candles, matches, and whistle
  • Radio with fresh and extra batteries
  • First aid kit with remedies for fever, LBM, minor wounds and pain, and maintenance medicines
  • Spare cash including coins
  • Items for special needs of young and older members of the family, including persons with disabilities
  • Easy-to-serve, ready-to-eat food enough for three days
  • Drinking water in sealed containers enough for three days
  • Mobile phones, powerbanks, and chargers
  • Clothing, raincoat, boots, and sanitary supplies
  • Sleeping bags or mats, and blankets
  • Ropes, old newspaper and ecobags made of strong materials


  1. The GO BAG items should be checked and replenished every three months.
  2. The GO BAG should be stored properly where it can be easily accessed in case of an emergency.
  3. Coordinate with leaders on community evacuation plan. Decide with the family where to meet in case there is a need to evacuate.
Source: Civil Defense PH (,
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