底层 /dǐcéng/ angolul

ground floor [ground floors]▼(floor of a building closest to ground level)
noun
[UK: ˈɡraʊnd.ˈflɔː] [US: ˈɡraʊnd.ˈflɔː]

underlying▼(basic or fundamental)
adjective
[UK: ˌʌn.də.ˈlaɪ.ɪŋ] [US: ˌʌn.dər.ˈlaɪ.ɪŋ]