An idea is a thought or conception, a product of mental activity. A notion is an idea in the most general sense, but the term usually suggests thoughts of more fleeting, vague, or imperfect kind. Whereas an idea can be something fairly worked out or elaborate, perhaps even a plan of action (The student has an idea for how to become an engineer), a notion is more like a whim or impulse—a flurry of thought that hasn't been seriously worked out. Perhaps this half-baked quality explains why notions are so often rejected, challenged, or dismissed! When used in the plural, notions can take on a whole new meaning: small items used in sewing, such as buttons, hooks, and ribbon.