strategy
Combos
Also: combinations, hand combinations, combinatorics
The number of distinct card combinations that make up a hand: 6 for any pocket pair, 4 for a suited hand, 12 for an offsuit hand, 16 for all suited and offsuit versions together.
Example. On a K-7-2 flop, an opponent holding 'any set' has 3+3+3 = 9 combos, while 'top pair' with A-K, K-Q and K-J has 36 combos.
Counting combos lets you weigh ranges precisely. If an opponent could have A-K (16 combos) or Q-Q (6 combos), they are ahead of your J-J much more often than a simple 'two hands' count suggests. Blockers change the count: holding one king reduces the combos of A-K from 16 to 12. Range analysis, blockers and solver outputs all rest on this arithmetic.