殊 is a bound morpheme (b.f.) that cannot stand alone as an independent word. It appears in formal or literary compounds, most commonly meaning 'special' (as in 特殊 tèshū 'special') or 'different' (as in 殊途同归 shū tú tóng guī 'different paths lead to the same destination'). You'll encounter it in fixed expressions and written Chinese, not in casual conversation.