単数
たんすう · tansuu · JLPT N2 · na-adj
singular (number)
1️⃣ 単数 = single number: 単 means one alone, 数 means number, so it's a count of exactly one.
単 (tan) means single or sole, and 数 (suu) means number. Together they name the grammatical form for one item, as opposed to 複数 (fukusuu), plural.
数 — 婁 (lóu, phonetic) + 攵 (action radical)
数 is a phono-semantic compound. The right side 攵 (a hand holding a stick) suggests an action, originally tallying or counting by striking marks. The left side 婁 supplies the sound. Over time the meaning broadened from 'to count' to 'number' and 'several'.