単 means “single, simple”

たん · tan

Also: one, merely

Kun'yomi (Japanese reading)
ひとえ
On'yomi (Chinese reading)
タン

JLPT N3 · Taught in grade 4 · 9 strokes

The story

Picture a single banner on its pole, three tassels on top: one thing standing alone. 単 is single and simple: 単語 is one word, the stuff of flashcards, 簡単 is easy, and 単位 is a unit, or a college credit.

Used in 簡単 (kantan, easy/simple), 単語 (tango, word), and 単位 (tan'i, unit/credit)

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