相比之下
xiāng bǐ zhī xià · HSK 7
by comparison
⚖️ 相比 (compare) + 之下 (under) = under comparison = by comparison
相 means mutual and 比 means to compare, so 相比 is to compare side by side. 之下 literally means under, here marking the frame: under that comparison, by comparison.
比 — two 匕 (person) side by side
比 is a pictograph showing two people standing side by side, facing the same direction. From this image of paired figures came the core meaning 'to compare' or 'to be next to,' since comparing things naturally involves placing them alongside each other.
之 — foot 止 above ground line 一
Originally a pictograph of a foot (止) stepping forward from a baseline, meaning 'to go' or 'to proceed'. Over time the concrete 'going' sense faded, and 之 was borrowed as a grammatical particle marking possession ('of') or as a pronoun ('it'), which became its dominant use in Classical Chinese.
下 — horizontal line 一 + mark below
下 is an indicative character: a long horizontal line represents a reference level, and a shorter stroke placed beneath it points to the area below. The original meaning 'below, down' comes directly from this spatial diagram, and it later extended to verbs like 'descend' and 'lower'.