非
fēi · HSK 4
not
🚫 非 = two wings facing opposite ways; opposing sides → 'not, wrong'
The character shows mirrored wings pointing away from each other, an etymology of opposition. From that 'against each other' sense it took on the meanings 'not', 'non-', and 'wrong'. Common in 非常 (extremely) and 非法 (illegal).
非 — two opposing wings 羽-like form
Originally a pictograph showing two wings spread in opposite directions, symbolizing things facing away from each other. From this 'opposition' image came the meaning 'not' or 'wrong.' It is also used as a phonetic component in many characters like 排, 悲, and 罪.