On  —prep. 1 (so as to be) supported by, attached to, covering, or enclosing (sat on a chair; stuck on the wall; rings on her fingers; leaned on his elbow). 2 carried with; about the person of (have you a pen on you?). 3 (of time) exactly at; during (on 29 may; on the hour; on schedule; closed on tuesday). 4 immediately after or before (i saw them on my return). 5 as a result of (on further examination).