- More generally, any result of mental activity; a thought, a notion; a way of thinking. [from 17th c.]
- (music) A musical theme or melodic subject. [from 18th c.]
- (philosophy) An abstract archetype of a given thing, compared to which real-life examples are seen as imperfect approximations; pure essence, as opposed to actual examples. [from 14th c.]
- An image of an object that is formed in the mind or recalled by the memory. [from 16th c.]
"The mere idea of you is enough to excite me."
- A vague or fanciful notion; a feeling or hunch; an impression. [from 17th c.]
"He had the wild idea that if he leant forward a little, he might be able to touch the mountain-top."
- (obsolete) The form or shape of something; a quintessential aspect or characteristic. [16th-18th c.]
- A conception in the mind of something to be done; a plan for doing something, an intention. [from 17th c.]
"I have an idea of how we might escape."
- (obsolete) The conception of someone or something as representing a perfect example; an ideal. [16th-19th c.]