Encyclopedic Entries

Best For
Grades 6-12+ (Ages 11+)

Subjects
Science

Appropriate For
T I F S 

An adaptation is a mutation, or genetic change, that helps an organism, such as a plant or animal, survive in its environment

Best For
Grades 5-12+ (Ages 10+)

Subjects
Social Studies, Science, Vocational Education, Geography

Appropriate For
T I F S 

Agriculture is the art and science of cultivating the soil, growing crops and raising livestock

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science

Appropriate For
T I F S 

Air is the invisible mixture of gases that surrounds the Earth. Air contains important substances, such as oxygen and nitrogen, that most species need to survive.

Best For
Grades 7-12+ (Ages 12+)

Subjects
Social Studies, Science, Geography

Appropriate For
T I F S 

An altimeter is a device that measures altitude, the distance of a point above sea level.

Best For
Grades 6-12+ (Ages 11+)

Subjects
Science, Geography

Appropriate For
T I F S 

Altitude, like elevation, is the distance above sea level

Best For
Grades 4-12+ (Ages 9+)

Subjects
Science, Geography

Appropriate For
T I F S K

An anemometer is an instrument that measures wind speed and wind pressure. Anemometers are important tools for meteorologists, who study weather patterns.

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science, Geography

Appropriate For
T I S 

Antarctica is a unique continent in that it does not have a native population.

Best For
Grades 6-12+ (Ages 11+)

Subjects
Social Studies, Science, Geography

Appropriate For
T I S 

Anthropology is the study of the origin and development of human societies and cultures.

Best For
Grades 4-12+ (Ages 9+)

Subjects
Science, Geography

Appropriate For
T I F S K

An aquifer is an underground layer of water-bearing rock. Water-bearing rocks are permeable, meaning that they have openings that liquids and gases can pass through.

Best For
Grades 5-12+ (Ages 10+)

Subjects
Social Studies, Science, Arts, Cross-Disciplinary, Geography

Appropriate For
T I F S 

Archaeology is the study of the human past using material remains. These remains can be any objects that people created, modified, or used.

Best For
Grades 4-12+ (Ages 9+)

Subjects
Science, Geography

Appropriate For
T I F S K

An archipelago is a group of islands closely scattered in a body of water. Usually, this body of water is the ocean, but it can also be a lake or river.

Best For
Grades 7-12+ (Ages 12+)

Subjects
Science, Geography

Appropriate For
T I F S K

The Arctic is the northernmost region of the Earth

Best For
Grades 6-12+ (Ages 11+)

Subjects
Geography

Appropriate For
T I F S 

Geographers use the term "area" to refer to any particular portion of the Earth’s surface

Best For
Grades 6-12+ (Ages 11+)

Subjects
Social Studies, Science, Geography

Appropriate For
T I F S K

An atlas is a book or collection of maps

Best For
Grades 7-12+ (Ages 12+)

Subjects
Science, Geography

Appropriate For
T I F S 

We live at the bottom of an invisible ocean called the atmosphere, a layer of gases surrounding our planet. Nitrogen and oxygen account for 99 percent of the gases in dry air, with argon, carbon dioxide, helium, neon, and other gases making up minute portions.

Best For
Grades 4-12+ (Ages 9+)

Subjects
Social Studies, Science, Geography

Appropriate For
T I F S 

An atoll is a ring-shaped coral reef, island, or series of islets. The atoll surrounds a body of water called a lagoon.

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science, Geography

Appropriate For
T I F S 

An aurora is a natural light display that shimmers in the sky. Auroras are only visible at night, and usually only appear in lower polar regions.

Best For
Grades 6-12+ (Ages 11+)

Subjects
Science

Appropriate For
T I F S 

An autotroph is an organism that can produce its own food using light, water, carbon dioxide, or other chemicals. Because autotrophs produce their own food, they are sometimes called producers.

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science, Geography

Appropriate For
T I F S 

During an avalanche, a mass of snow, rock, ice, soil, and other material slides swiftly down a mountainside. 

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science

Appropriate For
T I F S 

An axis is an invisible line about which an object rotates, or spins.

Best For
Grades 4-12+ (Ages 9+)

Subjects
Social Studies, Science, Health, Geography

Appropriate For
T I F S 

A bay is a body of water partially surrounded by land

Best For
Grades 4-12+ (Ages 9+)

Subjects
Social Studies, Science, Cross-Disciplinary

Appropriate For
T I F S 

A barometer is a tool used to measure atmospheric pressure, also called barometric pressure

Best For
Grades 6-12+ (Ages 11+)

Subjects
Science, Geography

Appropriate For
T I F S K

A basin is a depression, or dip, in the Earth’s surface

Best For
Grades 5-12+ (Ages 10+)

Subjects
Mathematics, Science, Geography

Appropriate For
T I F S 

Bathymetry is the measurement of the depth of water in oceans, rivers, or lakes. Bathymetric maps look a lot like topographic maps, which use lines to show the shape and elevation of land features.

Best For
Grades 5-12+ (Ages 10+)

Subjects
Social Studies, Science, Cross-Disciplinary, Geography

Appropriate For
T I F S 

A bathyscaphe is a self-propelled vehicle used for deep-sea dives

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science, Geography

Appropriate For
T I F S K

A bayou is a slow-moving creek or a swampy section of a river or a lake where the water is still.

Best For
Grades 3-12+ (Ages 8+)

Subjects
Science, Geography

Appropriate For
T I F S K

A beach is a narrow, gently sloping strip of land that lies along the edge of an ocean or a lake

Best For
Grades 5-12+ (Ages 10+)

Subjects
Science, Geography

Appropriate For
T I F S K

Bedrock is the relatively hard, solid rock beneath surface materials such as soil and gravel

Best For
Grades 4-12+ (Ages 9+)

Subjects
Science, Geography

Appropriate For
T I F S 

A bioblitz is an event that focuses on finding and identifying as many species as possible in a specific area over a short period of time, usually 24 hours.

Best For
Grades 6-12+ (Ages 11+)

Subjects
Science

Appropriate For
T I F S 

Biodiversity refers to all the different kinds of living organisms within a given area