The noun notion has 4 senses (first 3 from tagged texts)
1. (14) impression, feeling, belief, notion, opinion -- (a vague idea in which some confidence is placed; "his impression of her was favorable"; "what are your feelings about the crisis?"; "it strengthened my belief in his sincerity"; "I had a feeling that she was lying")
2. (14) notion -- (a general inclusive concept)
3. (2) notion, whim, whimsy, whimsey -- (an odd or fanciful or capricious idea; "the theatrical notion of disguise is associated with disaster in his stories"; "he had a whimsy about flying to the moon"; "whimsy can be humorous to someone with time to enjoy it")
4. notion -- ((usually plural) small personal articles or clothing or sewing items; "buttons and needles are notions")