| radicand |
in mathematics, the number, variable, or quantity under a radical sign. |
| radicchio |
a variety of chicory with slightly bitter, purplish red leaves that are used in salads. |
| radicle |
the lower part of a plant embryo or seedling, esp. the beginnings of a root. |
| radii |
a plural form of radius. |
| radio |
the sending of communications by means of electromagnetic waves in the frequency range from ten kilocycles to three hundred thousand megacycles. [9 definitions] |
| radio- |
radio. [3 definitions] |
| radioactive |
emitting energy or subatomic particles as a result of the decay of unstable isotopes. [2 definitions] |
| radioactive dating |
any of several methods of determining the age of an artifact, rock, or bone based on the known rate of decay of radioactive isotopes. |
| radioactivity |
the emission or amount of emission of energy or subatomic particles by the nuclei of certain unstable isotopes of elements as they decay. |
| radio astronomy |
the study of the universe by observation and analysis of extraterrestrial radio waves. |
| radio beacon |
a stationary source of radio waves that emits a distinctive signal as a navigational aid for ships and aircraft. |
| radiobiology |
the branch of biology concerned with the effects of radiation on living tissue and the use of radioactive tracers in the study of biological processes. |
| radiocarbon |
a radioactive isotope of carbon, esp. the isotope that has a nuclear mass of fourteen daltons and is often used in determining the age of various organic materials; carbon 14. |
| radiochemistry |
the branch of chemistry dealing with the study of radioactive elements. |
| radio compass |
a navigational aid consisting of a radio receiver that determines the transmission direction of incoming radio waves. |
| radiofrequency |
any frequency of electromagnetic waves between approximately ten kilohertz and 300 gigahertz, that can be used for radio transmission. |
| radio galaxy |
a galaxy that emits a large amount of radio energy. |
| radiogram |
a message transmitted using radio signals or wireless telegraph. [2 definitions] |
| radiograph |
an image produced by the action of x-rays or other forms of radiation on a photographic film; autoradiogram; radiogram. [2 definitions] |
| radioisotope |
an unstable isotope that emits subatomic particles or energy in decaying to a more stable state. |
| radiolarian |
any small marine protozoan having an amoebalike body encased in a silica skeleton. |