白天
bái tiān · HSK 1
daytime
☀️ 白 (white/bright) + 天 (sky/day) = the bright part of the day
白 means white or bright; 天 means sky or day. Together they literally read as bright-sky, the lit half of the 24-hour cycle. Contrast with 夜晚 (yèwǎn, nighttime).
白 — pictograph; resembles 日 (sun) with a stroke on top
白 is generally considered a pictograph, traditionally explained as depicting the sun rising with a ray of light above it, hence the meaning 'white' or 'bright.' Some scholars instead see it as a drawing of a thumbnail or an acorn. From 'bright' it extended to 'clear,' 'plain,' and 'to state plainly.'
天 — 一 (one/sky) above 大 (big person)
Originally a pictograph of a person (大) with an emphasized head, representing what is above — the sky or heavens. The top stroke evolved into 一, symbolizing the vast expanse overhead. From 'sky' it extended to mean 'day,' 'heaven,' and 'nature.'