二 two

as in, "Vince NEIL has two chins."

two people ★★★★★ FP
二 (two) + 人 (person) = 二人 (two people)

February ★★★★★ KANA
二 (two) + 月 (moon) = 二月 (February)

hangover ★★★★☆ SARC
二 (two) + 日 (sun, day) + 酔 (drunk) = 二日酔い (hangover)

hangover (literally: 'paying for your drink'）

second day of the month ★★★★☆
二 (two) + 日 (sun, day) = 二日 (second day of the month)

double-xxx ★☆☆☆☆ PRE
二 (two) + 重 (heavy / overlap) = 二重 (double-xxx)

PREFIX meaning double, as in "double-chin" or "twin-engine plane."