Idea

The transcript, image, or picture of a visible object, that is formed by the mind; also, a similar image of any object whatever, whether sensible or spiritual.

A general notion, or a conception formed by generalization.

Hence: Any object apprehended, conceived, or thought of, by the mind; a notion, conception, or thought; the real object that is conceived or thought of.

A belief, option, or doctrine; a characteristic or controlling principle; as, an essential idea; the idea of development.

A plan or purpose of action; intention; design.

A rational conception; the complete conception of an object when thought of in all its essential elements or constituents; the necessary metaphysical or constituent attributes and relations, when conceived in the abstract.

A fiction object or picture created by the imagination; the same when proposed as a pattern to be copied, or a standard to be reached; one of the archetypes or patterns of created things, conceived by the Platonists to have excited objectively from eternity in the mind of the Deity.

the content of cognition; the main thing you are thinking about; "it was not a good idea"; "the thought never entered my mind"

(music) melodic subject of a musical composition; "the theme is announced in the first measures"; "the accompanist picked up the idea and elaborated it"