意

Bottom heart radical (Kangxi #61) - the indexing radical, a stylised picture of the heart organ. Anchors the mental-state semantics: 意 covers ideas, intentions, thoughts, meaning, will (注意 attention, 意见 opinion, 同意 agree, 主意 plan). Same radical groups 想, 念, 怎, 思 - the bottom-position 心 family of mental verbs.

Top 音 (sound) - provides the semantic anchor: thoughts and intentions are the unspoken sounds of the heart. The compound is a classic 会意 (compound ideograph): sound (音) over heart (心) = the heart's sound = idea, intention, meaning. Same 音 standalone means 'sound, tone, music.'