痴 means “foolish, obsessed”

ち · chi

Also: stupid

Kun'yomi (Japanese reading)
しれる, おろか
On'yomi (Chinese reading)
チ

JLPT N1 · Taught in secondary school · 13 strokes

The story

Sickness (疒) over knowing (知): knowledge itself gone sick. 痴 is foolishness and blind obsession: 愚痴 is grumbling, 音痴 is tone-deaf, 方向音痴 hopeless with directions, and 痴漢 is a train groper, the reason for women-only cars.

Used in 愚痴 (guchi, grumbling), 音痴 (onchi, tone-deaf), and 痴漢 (chikan, groper)

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Readings from KANJIDIC2, © EDRDG, CC BY-SA.