A treble is a multi-selection bet linking three individual picks into one wager. All three selections must win for the bet to pay out. The odds multiply across all three legs, making the potential return considerably larger than any single selection — but also meaning that a single loss kills the entire bet.
How the returns roll over: imagine a chain reaction. The stake is placed on Selection 1. If it wins, the full return (stake × odds) becomes the new stake on Selection 2. If Selection 2 wins, its full return becomes the stake on Selection 3. The final return is Stake × Odds1 × Odds2 × Odds3.
Treble vs three singles: for the same total stake, three singles give partial returns when only one or two selections win. A treble requires all three to win but pays more when they do. Three £10 singles is £30 staked with partial recovery possible; a £10 treble is £10 staked with no partial recovery — all or nothing.
Horse racing trebles often target competitive markets where the bookmaker's margin is lower. Combining three shorter-priced selections in a treble (e.g. three 2.0 shots) gives combined odds of 8.0 — a useful multiplication without requiring a heroic upset. The risk is that even short-priced selections lose regularly.
Example
Saturday racing: You pick three horses at 2.50, 3.00, and 2.00. Combined treble odds = 2.50 × 3.00 × 2.00 = 15.0. A £10 treble stake. The first two horses win; the third horse finishes second. The entire bet loses — £10 gone. Three separate £10 singles would have returned £25 + £30 = £55 profit from two winners, only losing the £10 on the third.