代 means “generation, substitute”

だい · dai

Also: change, convert, replace

Kun'yomi (Japanese reading)
かわる, かわり, かえる, よ, しろ
On'yomi (Chinese reading)
ダイ, タイ

JLPT N4 · Taught in grade 3 · 5 strokes

The story

One person standing in another's place, marked by a tally stake: the substitute who carries the line forward. 代 stretches across Japanese time: 時代 the eras of history, 十代 the teenage years.

Used in 時代 (jidai, era), 代わり (kawari, substitute), and 電気代 (denkidai, electricity bill)

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