Definition
A bet that turns your selections into several smaller accumulators so that you can still win something if some selections lose. Each combination costs a stake.
System bets are named by how many selections must win in each combination and how many selections there are in total, such as "2/3", "3/4" or "2/5". Some bookmakers also offer named systems (for example a "Trixie", which is three doubles plus one treble).
The key thing to understand is the total cost. Every combination is a separate bet with its own stake. A "2 from 5" system has ten doubles; at $0.50 each, that is $5.00 in total. The slip normally shows the number of combinations and the total stake: always check it before confirming.
System bets reduce the "all or nothing" risk of a single accumulator, but they do not remove the bookmaker's margin, and you can win some combinations while still losing money overall. Use the accumulator calculator to price individual combinations.