小

小 (xiǎo) is the adjective 'small,' the opposite of 大 (dà, 'big'). It covers physical size (小猫 'small cat,' 小房子 'small house'), age in the sense of 'young' (他比我小 'he's younger than me'), and works as a prefix for nicknames and affectionate forms (小李 'Little Li / young Mr. Li').

Two things English speakers should know: first, 小 + surname is a very common informal way to address younger colleagues or friends — 小王, 小张 — roughly 'young Wang / Zhang'; flipping it with 老 + surname (老王 'old Wang') addresses older or familiar people respectfully; second, 小 is not the same as 少 — 小 is about SIZE, while 少 (shǎo) is about QUANTITY. 'A small amount' uses 少