后备
hoù bèi · HSK 7
reserve
🔋 后 (behind/rear) + 备 (prepare/equip) = kept ready in the rear = a reserve
后 means behind or rear; 备 means to prepare or equip. Something prepared and held at the rear is your backup or reserve, like a spare battery waiting behind the front line.
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.