星期日
Xīng qī rì · HSK 1
Sunday
☀️ 星期 (week) + 日 (sun/day) = the sun's day of the week = Sunday
日 means sun and also day. Many cultures name Sunday after the sun (English Sun-day, German Sonntag). 星期 literally means star-period, the Chinese word for week.
期 — 其 (phonetic) + 月 (moon/time)
期 is a phono-semantic compound. The right side 月 (moon) signals meaning, since lunar cycles marked fixed time periods in ancient China. The left side 其 supplies the sound. Together it points to a set time, period, or appointed date — meanings still carried today in words like 期间 and 日期.
日 — pictograph of the sun
日 is a pictograph of the sun, originally drawn as a circle with a dot or stroke inside representing the sun's substance. Over time the round shape was squared off into the modern rectangular form. It means 'sun' and by extension 'day'.