| radiate |
to come out in the form of rays or waves. [4 definitions] |
| radiation |
When we talk about radiation, we mean particles or waves of energy that are sent out by sources of heat or light. Sunlight is a form of radiation, for example. Some forms of radiation are dangerous. Even sunlight can be bad if people get too much of it. |
| radiator |
a device that uses steam or hot water passing through pipes in order to heat a room. [2 definitions] |
| radical |
having to do with the root or source; basic; fundamental. [4 definitions] |
| radii |
a plural of "radius." |
| radio |
A radio is something that receives invisible signals from another location and changes them into sound. People use a radio to listen to music, the news, and other programs. [2 definitions] |
| radioactive |
giving off energy as a result of the decay of unstable atoms. |
| radioactivity |
the giving off of energy as a result of the decay of unstable atoms. |
| radish |
a plant that has a crisp and strong-tasting root. [2 definitions] |
| radium |
a silver-white, radioactive metal that is one of the chemical elements. Radium glows in the dark. It is used to treat cancer. (symbol: Ra) |
| radius |
a straight line from the center to the edge of a circle or sphere. [2 definitions] |
| radon |
a radioactive gas that is one of the chemical elements. It is found in small amounts in some soils and rocks. (symbol: Rn) |
| raffle |
A raffle is a kind of simple contest. People buy tickets, usually at the beginning of some event, and when all the tickets are collected, someone reaches into the collection of tickets and pulls out a winning ticket. The person who bought that ticket wins a prize. The money that comes from selling the raffle tickets, is often used to raise money for a good cause. |
| raft1 |
A raft is a flat object that people make so that it floats on water. A raft is often made of pieces of wood or empty barrels. Rafts can be used to carry people or things. [3 definitions] |
| rag1 |
A rag is a small piece of cloth often cut or torn from a larger piece of cloth. [2 definitions] |
| rag2 |
(informal) to tease or scold. |
| rage |
Rage is very great anger. If someone is in a rage, they are extremely angry. [4 definitions] |
| ragged |
worn down into rags; torn. [4 definitions] |
| ragtime |
Ragtime is a kind of music that developed in the late nineteenth and early twentieth century in the United States. Ragtime is usually written for the piano and has a bouncy kind of rhythm. It was very popular in the 1910s and 1920s, and people liked to dance to it. |
| ragweed |
a weed that produces a large amount of pollen in the fall. Many people are allergic to ragweed. |
| raid |
A raid is a sudden surprise attack. [3 definitions] |