| air conditioning |
a system that cools air and takes dust and dampness out of it. Air conditioning is used inside buildings and cars. |
| airline |
a system of transportation that allows people to fly from one place to another, or a business that owns and operates the equipment to do this. |
| binary |
pertaining to a numbering system with a base of two. [1/2 definitions] |
| binary system |
a numbering system with a base of two. In binary numbers, any number can be expressed by 1, 0, or a combination of these. The number five is written as "101" in the binary system. |
| boot |
to start up by loading the operating system of or giving the first instructions to a computer. [1/4 definitions] |
| bowel |
(usually plural) the long tube below the stomach that forms part of the digestive system; intestine. |
| Braille |
(often lowercase) a writing and printing system for blind people, in which patterns of raised dots are used to represent letters. Blind people touch the dots with their fingers to read. |
| brain |
the organ inside the skull of humans and animals. The brain is the main part of the central nervous system. It controls the body's movements and activities and is the center of thought, memory, and feelings. [1/3 definitions] |
| caffeine |
a bitter substance found in coffee, tea, chocolate, and some sodas. Caffeine stimulates the heart and nervous system and can cause a person to stay awake and alert. |
| capitalism |
an economic system in which land, factories, and other resources are owned by individuals instead of the government. In this system, the prices of things we buy are decided by the people who sell them and not by the government. |
| circulate |
to move or flow along a closed path or system. [1/2 definitions] |
| circulatory |
of or pertaining to the circulatory system, the system of bodily organs, including the heart, arteries, and veins, that send blood and lymph throughout the body and return it to the heart. |
| circulatory system |
a system in the body made up of the heart, blood vessels, blood, and lymph vessels that carries blood and lymph around the body. |
| civilization |
an advanced state of development of a society as judged by such things as having a system of government and laws, using a written language, and keeping written records. [1/2 definitions] |
| civil service |
any branch of government that is not part of the legislature, court system, or the military. |
| code |
a system of symbols or signals used in place of letters and numbers for sending messages. [2/3 definitions] |
| communism |
(sometimes capitalized) a system of government in which all factories, farms, and natural resources are owned in common. |
| computer language |
a system of words and symbols that is used to program a computer; code. There are hundreds of computer languages, such as C, Cheetah, and JavaScript. |
| constitution |
(sometimes capitalized) the written record of such a system. [1/3 definitions] |
| coral reef |
a structure that rises up from the bottom of the sea and is made up of the hard skeletons of tiny sea animals called corals. Coral reefs are found in warm, shallow sea waters around the world. The largest system of coral reefs is found in the Coral Sea off the northeastern coast of Australia. |
| crop |
a pouch in the digestive system of a bird, between its mouth and stomach. The crop stores food and prepares it for digestion. [1/7 definitions] |