noun
win bet; win-only betting
A type of bet in horse racing, boat racing, or bicycle racing where you predict the first-place finisher. Often contrasted with 複勝式 (place bet) and other exotic wagers.
競馬で単勝式の馬券を買った。
I bought a win ticket at the horse races.
単勝式は初心者にもわかりやすい賭け方
Win betting is an easy-to-understand wager even for beginners.
馬券 is the general term for a betting ticket in horse racing; 単勝式 is a specific type of bet.
Compound of 単 (single) + 勝 (win) + 式 (style/system), literally 'single-win system'. The term is transparently derived from its kanji components.