Merriam-Webster Collegiate Dictionary - idea

 noun  Etymology: Middle English, from Latin, from Greek, from idein to see — more at wit  Date: 14th century  1.  a. a transcendent entity that is a real pattern of which existing things are imperfect representations  b. a standard of perfection ; ~l  c. a plan for action ; design  2. archaic a visible representation of a conception ; a replica of a pattern  3.  a. obsolete an image recalled by memory  b. an indefinite or unformed conception  c. an entity (as a thought, concept, sensation, or image) actually or potentially present to consciousness  4. a formulated thought or opinion  5. whatever is known or supposed about something a child's ~ of time  6. the central meaning or chief end of a particular action or situation  7. Christian Science an image in Mind  • ~less adjective Synonyms:  ~, concept, conception, thought, notion, impression mean what exists in the mind as a representation (as of something comprehended) or as a formulation (as of a plan). ~ may apply to a mental image or formulation of something seen or known or imagined, to a pure abstraction, or to something assumed or vaguely sensed innovative ~s my ~ of paradise. concept may apply to the ~ formed by consideration of instances of a species or genus or, more broadly, to any ~ of what a thing ought to be a society with no concept of private property. conception is often interchangeable with concept; it may stress the process of imagining or formulating rather than the result our changing conception of what constitutes art. thought is likely to suggest the result of reflecting, reasoning, or meditating rather than of imagining commit your thoughts to paper. notion suggests an ~ not much resolved by analysis or reflection and may suggest the capricious or accidental you have the oddest notions. impression applies to an ~ or notion resulting immediately from some stimulation of the senses the first impression is of soaring height.