之下
zhīxià · HSK 5
under
⬇️ 之下 = zhī (of/that) + xià (below) — literally 'below of'
之 is a classical particle linking modifier to noun; 下 means below or under. Together 之下 functions like 'under the [condition/category] of', a fixed pattern after a noun phrase to mean beneath or subject to it.
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'.