Literary and classical. 权舆 originally referred to the early sprouts of plants, then was extended to mean 'the beginning of anything'. The phrase appears in 《诗经·秦风》: 'Yú jiē hū bù chéng quányú' (alas, things never reach their early promise).
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Strongly literary; you will only see it in formal essays, academic writing, or classical Chinese — never in conversation.
