v.1. To place a bet of some amount on some event: I bet $5 on the first race of the evening. I'm not going to bet on the last race.
2. To place a bet of some amount on some participant in an event: We bet $200 on the home team, but they lost. Don't bet anything on me in this game; I'm not a very good player. Will you bet on any of the players?
3. To expect or feel sure that something will happen: You can bet on Chris being late to the meeting.