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1. Something, such as a thought or conception, that is the product of mental activity.
2. An opinion, conviction, or principle: has some strange political ideas.
3. A plan, purpose, or goal: She started school with the idea of becoming a doctor.
4. The gist or significance: The idea of the article is that investing in green technology can save you money in the long run.
5. A sense that something can happen; a notion or expectation: They have this idea that we can just drop what we're doing and go to the park.
6. Music A theme or motif.
7. Philosophy
a. In the philosophy of Plato, a non-physical form or archetype to which beings in phenomenal reality correspond only as imperfect replicas.
b. In the philosophy of Kant, a concept of reason that is transcendent but nonempirical.
c. In the philosophy of Hegel, absolute truth; the complete and ultimate product of reason.
8. Obsolete A mental image of something remembered.

[Middle English, from Latin, from Greek; see weid- in the Appendix of Indo-European roots.]

i·de′a·less adj.
Synonyms: idea, thought, notion, concept, conception
These nouns refer to what is formed or represented in the mind as the product of mental activity. Idea has the widest range: "Human history is in essence a history of ideas" (H.G. Wells).
Thought is distinctively intellectual and stresses contemplation and reasoning: She gathered her thoughts before she spoke. Notion suggests an often intuitive idea or image conceived by the mind: "All that came to mind was a notion of galactic space, of spirals, the Horse Nebula, all of which were distant and mysterious and cold" (Craig Nova).
Concept and conception are applied to mental formulations on a broad scale: You seem to have absolutely no concept of time. "Every succeeding scientific discovery makes greater nonsense of old-time conceptions of sovereignty" (Anthony Eden).
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
References in periodicals archive ?
She also slammed the BJP, saying they were a incompetent, leaderless and idealess party that only believed in maligning the image of other political parties.
The opposition assessed Ivanov's first annual address, since being elected president, as empty, idealess but filled with compliments to the Government.
This suits the idealess opposition as well, so it does not risk an even worse result," says Popovski.