電球
でんきゅう · denkyuu · JLPT N2 · noun
light bulb
💡 電 (electricity) + 球 (ball) = electric ball, the light bulb
電 means electricity and 球 means ball or sphere. Together, 電球 (denkyuu) is an electric ball: the bulb that lights up when current flows through it.
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'.