Origin unclear. Various explanations include (1) depicting three leaves on branches of a tree, a remnant from the top part of 枼 (leaf), which was phonetically similar in Old Chinese, (2) three dots added above the phonetically similar 止 (zhǐ - foot), or (3) three copies of 十 (ten), similar to the archaic character 卅 (thirty), depicting a 30-year generation.

Evolution

Bronze script

Early Western Zhou (~1000 BC)

Seal script

Shuowen (~100 AD)

Clerical script

Eastern Han dynasty (25-220 AD)

Regular script

Modern

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