欠 means “lack, absent, chip”

けつ · ketsu

Also: gap, fail, yawning radical (no. 76)

Kun'yomi (Japanese reading)
かける, かく
On'yomi (Chinese reading)
ケツ, ケン

JLPT N3 · Taught in grade 4 · 4 strokes

The story

A person with mouth wide open: 欠 began as a picture of a yawn. Now it marks a gap or something missing: 欠席 is an absence from class, 欠点 is a flaw, and a chipped cup is 欠けている.

Used in 欠席 (kesseki, absence), 欠点 (ketten, flaw), and 欠ける (kakeru, to be chipped/missing)

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