一変

いっぺん · ippen · JLPT N1 · noun

change

🦋 一 (one) + 変 (change) = one total change: the whole thing transforms in one go

一 here means 'whole' or 'all at once', so 一変 is a change that covers everything, not a small adjustment. The butterfly stands for a full transformation.

一 — single horizontal stroke
一 is one of the simplest pictographs in Chinese, depicting a single horizontal line to represent the number one. It has retained essentially the same form since oracle bone script over 3,000 years ago. By extension it also means 'first,' 'whole,' or 'same.'

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