底下
dǐxià · HSK 3
under
⬇️ 底 = bottom + 下 = below; bottom-below = underneath
底 means base or bottom of something; 下 means down or below. Together 底下 literally stacks bottom + below to mean under or beneath. Common for spatial relations: 桌子底下 = under the table.
底 — 广 (shelter radical) + 氐 (phonetic 'dǐ')
底 is a semantic-phonetic compound. The 广 radical depicts a roofed structure or shelter, suggesting the bottom or base of a building. The component 氐 supplies the sound 'dǐ' and originally meant 'low' or 'base,' reinforcing the meaning. Together they convey 'bottom,' 'foundation,' or 'underneath.'
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'.