[ahy-dee-uh, ahy-deeuh]
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  1. any conception existing in the mind as a result of mental understanding, awareness, or activity.
  2. a thought, conception, or notion: That is an excellent idea.
  3. an impression: He gave me a general idea of how he plans to run the department.
  4. an opinion, view, or belief: His ideas on raising children are certainly strange.
  5. a plan of action; an intention: the idea of becoming an engineer.
  6. a groundless supposition; fantasy.
  7. Philosophy.
    1. a concept developed by the mind.
    2. a conception of what is desirable or ought to be; ideal.
    3. (initial capital letter)Platonism.Also called archetype or pattern of which the individual objects in any natural class are imperfect copies and from which they derive their being.
    4. Kantianism.idea of pure reason.
  8. Music. a theme, phrase, or figure.
  9. Obsolete.
    1. a likeness.
    2. a mental image.

Origin of idea

1400–50; < Late Latin < Greek idéā form, pattern, equivalent to ide- (stem of ideîn to see) + feminine noun ending; replacing late Middle English idee < Middle French < Late Latin, as above; akin to wit1
Related formsi·de·a·less, adjectivepre·i·de·a, nounsub·i·de·a, noun

Synonyms for idea

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1, 2. Idea, thought, conception, notion refer to a product of mental activity. Idea, although it may refer to thoughts of any degree of seriousness or triviality, is commonly used for mental concepts considered more important or elaborate: We pondered the idea of the fourth dimension. The idea of his arrival frightened me. Thought, which reflects its primary emphasis on the mental process, may denote any concept except the more weighty and elaborate ones: I welcomed his thoughts on the subject. A thought came to him. Conception suggests a thought that seems complete, individual, recent, or somewhat intricate: The architect's conception delighted them. Notion suggests a fleeting, vague, or imperfect thought: a bare notion of how to proceed. 4. sentiment, judgment. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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British Dictionary definitions for idea


  1. any content of the mind, esp the conscious mind
  2. the thought of somethingthe very idea appals me
  3. a mental representation of somethingshe's got a good idea of the layout of the factory
  4. the characterization of something in general terms; conceptthe idea of a square circle is self-contradictory
  5. an individual's conception of somethinghis idea of honesty is not the same as yours and mine
  6. the belief that something is the casehe has the idea that what he's doing is right
  7. a scheme, intention, plan, etchere's my idea for the sales campaign
  8. a vague notion or indication; inklinghe had no idea of what life would be like in Africa
  9. significance or purposethe idea of the game is to discover the murderer
  10. philosophy
    1. a private mental object, regarded as the immediate object of thought or perception
    2. a Platonic Idea or Form
  11. music a thematic phrase or figure; motif
  12. obsolete a mental image
  13. get ideas to become ambitious, restless, etc
  14. not one's idea of not what one regards as (hard work, a holiday, etc)
  15. that's an idea that is worth considering
  16. the very idea! that is preposterous, unreasonable, etc
Derived Formsidealess, adjective

Word Origin for idea

C16: via Late Latin from Greek: model, pattern, notion, from idein to see


It is usually considered correct to say that someone has the idea of doing something, rather than the idea to do it: he had the idea of taking (not the idea to take) a short holiday


  1. another name for Form
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for idea

late 14c., "archetype of a thing in the mind of God; Platonic `idea,'" from Latin idea "idea," and in Platonic philosophy "archetype," from Greek idea "ideal prototype," literally "the look of a thing (as opposed to the reality); form; kind, sort, nature," from idein "to see," from PIE *wid-es-ya-, suffixed form of root *weid- "to see" (see vision). Sense of "result of thinking" first recorded 1640s.

Men of one idea, like a hen with one chicken, and that a duckling. [Thoreau, "Walden"]

Idée fixe (1836) is from French, literally "fixed idea."

Online Etymology Dictionary, © 2010 Douglas Harper

idea in Medicine


  1. Something, such as a thought or conception, that potentially or actually exists in the mind as a product of mental activity.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Idioms and Phrases with idea


see bright idea; put ideas in someone's head; what's the idea.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.