| abscess |
a sore that forms within the tissues of the body and is filled with pus. Abscesses can be caused by an infection. |
| ace |
a serve in tennis that wins a point because the other player can not reach the ball. [1/5 definitions] |
| acrobat |
a person who can do physical acts that take balance and skill. |
| address |
to write information on, telling where something can be delivered. [1/6 definitions] |
| adenoid |
(usually plural) a mass of tissue that grows behind the nose in the upper part of the throat. When swollen, the adenoids can make breathing difficult. |
| aircraft |
any machine that can fly through the air, such as an airplane, helicopter, glider, or balloon. |
| aircraft carrier |
a very large ship with a flat deck on which airplanes can take off and land. |
| airplane |
a machine that can fly because of the force of air upon its wings; plane. An airplane is driven by propellers or a jet engine. |
| airport |
a large area of level land where airplanes can land and take off. |
| airship |
an aircraft that is lighter than air and can be steered. An airship has an engine and is filled with gas. |
| alarm clock |
a clock with a bell or buzzer that can be set to sound at a particular time. |
| albino |
a human or animal that is born without normal coloring. Albinos have very pale skin and hair and pink eyes. Plants can also be albinos. |
| album |
a book with blank pages or empty pockets in which a collection can be placed. An album can hold photographs, stamps, or mementos. [1/2 definitions] |
| alcohol |
a clear liquid that burns easily and can be made from certain grains and fruits. Alcohol is present in such drinks as beer, wine, and whiskey. It is also used in making medicines and chemicals. [1/2 definitions] |
| allergy |
a condition in which a person's body has an unusual reaction to certain things. An allergy can cause itching, coughing, sneezing, or trouble breathing. Allergies to animal hair, pollen, and certain foods are among the most common. |
| almond |
a small tree related to the cherry tree that grows in warm areas and produces seeds that can be eaten. [1/3 definitions] |
| aloud |
in a voice that can be heard; not in a whisper. |
| ammunition |
the objects fired from any weapon, or material that can be exploded. Bullets, bombs, and gunpowder are types of ammunition. [1/2 definitions] |
| amoeba |
a tiny living thing made of only one cell. Amoebas move by changing their shape. They eat by wrapping their bodies around their food. Amoebas live in fresh and salt water, soil, and in animals. Most kinds of amoebas can only be seen through a microscope. |
| amphibian |
a small animal that spends part of its life cycle in water and part of its life cycle on land. Amphibians hatch in water and breathe with gills. Then they develop lungs so the adults can breathe air. Amphibians are cold-blooded animals with skeletons inside their bodies. Frogs, toads, and salamanders are amphibians. [2 definitions] |
| anaconda |
a very large snake found in South America. Anacondas are not poisonous but kill other animals by squeezing them until they cannot breathe. Anacondas can grow to over twenty feet long. |