思前想后
sī qián xiǎng hoù · HSK 7
to consider past cause and future effect
⏮️⏭️ 思 think + 前 before + 想 think + 后 after = weigh the before and the after
Two think-verbs (思, 想) bracket two direction words: 前 before/front and 后 after/back. The pattern A前B后 means spanning both ends, so this idiom is thinking back over causes and forward to consequences.
前 — top 丷 + 一 + 月 (moon) + 刂 (knife)
Originally written 歬, depicting a foot 止 above a boat 舟, meaning to advance or go forward. Over time the form evolved and the knife radical 刂 was added, while 止 and 舟 fused into the modern shape. The core meaning 'front, before, ahead' has stayed consistent.
想 — heart 心 + 相 (xiāng, phonetic)
想 is a semantic-phonetic compound. The heart radical 心 at the bottom carries the meaning, since classical Chinese located thought and feeling in the heart. The top component 相 (xiāng) supplies the sound, and over time the character settled into the senses 'to think,' 'to want,' and 'to miss.'
后 — 厂 cliff + 一 + 口 mouth
Originally depicted a ruler or sovereign issuing commands, showing a figure with a mouth giving orders. It came to mean 'queen' or 'empress.' In modern simplified Chinese, 后 also absorbed the meaning 'behind/after' from the traditional character 後, so context decides which sense applies.