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activity

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ac⋅tiv⋅i⋅ty

  [ak-tiv-i-tee]
Use activity in a Sentence
–noun, plural -ties.
1. the state or quality of being active: There was not much activity in the stock market today. He doesn't have enough physical activity in his life.
2. a specific deed, action, function, or sphere of action: social activities.
3. work, esp. in elementary grades at school, that involves direct experience by the student rather than textbook study.
4. energetic activity; animation; liveliness.
5. a use of energy or force; an active movement or operation.
6. normal mental or bodily power, function, or process.
7. Physical Chemistry. the capacity of a substance to react, corrected for the loss of reactivity due to the interaction of its constituents.
8. Physics.
a. the number of atoms of a radioactive substance that disintegrate per unit of time, usually expressed in curies.
b. radioactivity.
9. an organizational unit or the function it performs.
Origin:
1520–30; (< MF) < ML āctīvitās. See active, -ity
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ra⋅di⋅o⋅ac⋅tiv⋅i⋅ty

  [rey-dee-oh-ak-tiv-i-tee]
–noun Physics, Chemistry.
the phenomenon, exhibited by and being a property of certain elements, of spontaneously emitting radiation resulting from changes in the nuclei of atoms of the element.
Also called activity.

Origin:
1895–1900; radio- + activity
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2009.
Cite This Source Link To activity
ac·tiv·i·ty   (āk-tĭv'ĭ-tē)   
n.   pl. ac·tiv·i·ties

  1. The state of being active.

  2. Energetic action or movement; liveliness.

    1. A specified pursuit in which a person partakes.

    2. An educational process or procedure intended to stimulate learning through actual experience.

  4. The intensity of a radioactive source.

  5. The ability to take part in a chemical reaction.

  6. A physiological process: respiratory activity.

The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2009 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Cultural Dictionary

radioactivity

The emission of elementary particles by some atoms when their unstable nuclei disintegrate (see half-life). Materials composed of such atoms are radioactive. (See alpha radiation, beta radiation, and gamma radiation.)

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Financial Dictionary

activity

The amount of relative trading volume in a security.

Wall Street Words: An A to Z Guide to Investment Terms by David L. Scott.
Copyright © 2003. Published by Houghton Mifflin.
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Medical Dictionary

Main Entry: ac·tiv·i·ty
Pronunciation: ak-'tiv-&t-E
Function: noun
Inflected Form: plural -ties
1 : natural or normal function: as a : a process (as digestion) that an organism carries on or participates in by virtue of being alive b : a similar process actually orpotentially involving mental function; specifically : an educational procedure designed to stimulate learning by firsthand experience
2 : the characteristic ofacting chemically or of promoting a chemical reaction activity of a catalyst>

Main Entry: ra·dio·ac·tiv·i·ty
Pronunciation: -ak-'tiv-&t-E
Function: noun
Inflected Form: plural -ties
: the property possessed by some elements (as uranium) or isotopes (as carbon 14) of spontaneously emitting energetic particles (as electrons or alpha particles) by the disintegration of theiratomic nuclei
Merriam-Webster's Medical Dictionary, © 2002 Merriam-Webster, Inc.
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Medical Dictionary

activity ac·tiv·i·ty (āk-tĭv'ĭ-tē)
n.

  1. A physiological process.

  2. The presence of neurogenic electrical energy in electroencephalography..

  3. An ideal concentration for which the law of mass action will apply perfectly.

  4. The intensity of a radioactive source.

  5. The ability to take part in a chemical reaction.

radioactivity ra·di·o·ac·tiv·i·ty (rā'dē-ō-āk-tĭv'ĭ-tē)
n.

  1. Spontaneous emission of radiation, either directly from unstable atomic nuclei or as a consequence of a nuclear reaction.

  2. The radiation, including alpha particles, nucleons, electrons, and gamma rays, emitted by a radioactive substance.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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