月球
yuè qiú · HSK 5
moon
🌙 月 (moon) + 球 (ball/sphere) = moon-ball, the celestial sphere
月 means moon and 球 means ball or sphere (same 球 as in 地球 earth-ball and 足球 foot-ball). So 月球 literally reads moon-sphere, the formal/astronomical word for the Moon as a body.
月 — pictograph of crescent moon
月 is a pictograph of a crescent moon, chosen over a full circle to distinguish it from 日 (sun). The inner strokes originally depicted the moon's shadow or markings. As a radical it often relates to the moon, time, or (via a lookalike form of 肉 'flesh') body parts.
球 — jade radical 玉/王 + qiu 求 (phonetic)
球 is a semantic-phonetic compound. The left side 王 is the 'jade' radical, indicating the original meaning: a fine piece of jade or a jade ornament. The right side 求 supplies the sound 'qiu'. Over time the meaning broadened from a jade sphere to any round object, and today it most commonly means 'ball' or 'globe'.