The Number of Players
The number of players contesting a pot determines the kinds of hands that are playable. The irony is that you can play weaker starting cards when many players contest the pot, but you must have a stronger final hand at showdown. A high pair is a strong favorite to win against one or two opponents, but if ten players enter the hand, someone is likely to beat a high pair with a flush or a straight. Conversely, drawing hands (weak initial cards that may give you a flush or straight) are playable against a large field since the final pot will be large, but drawing hands are seldom worth playing for small pots against one or two players.