During NBA regular seasons, teams aren't permitted to carry more than 15 players on their rosters, except in rare instances. Generally, when a club with 15 players on its roster acquires a new player, it must waive someone to clear a spot.
In the offseason, however, teams are permitted to carry up to 20 players on their rosters. One club taking advantage of that extra flexibility this summer is the Houston Rockets -- even after Houston hit the 20-man limit, it continued to pursue free agents. When the Rockets signed Carlos Delfino, they waived Josh Harrellson to remain at 20 players, and later waived Sean Williams to clear a roster spot for Scott Machado.
Many of the Rockets' players are on non-guaranteed deals, making it likely that those guys will simply be waived before the regular season begins so that the team can reduce its roster to the in-season limit of 15 players. However, Houston (or any other team) is allowed to carry more than 15 guaranteed contracts until the season starts, if it so chooses.
According to Doug Smith of the Toronto Star, for instance, the Raptors' deals with Jamaal Magloire and Dominic McGuire will both be at least partially guaranteed. Toronto already had 14 players on guaranteed contracts, meaning the Raptors will likely head into training camp carrying 16 players with some form of guarantee. So even if non-guaranteed camp invitee Chris Wright doesn't earn a roster spot, the Raps will have to either trade a player or eat some salary to reduce their roster to 15 players by opening night.
Before the season begins, teams like the Rockets and Raptors, who are carrying more than 15 players, will be required to make cuts. However, other clubs may have to worry about meeting the roster minimum, rather than getting below the maximum.
The 76ers are one of a handful of clubs that are only carrying 13 players, which is the fewest an NBA can have on its roster. Philadelphia's 13th man, Maalik Wayns, is on a non-guaranteed contract, but is currently in great position to make the team -- the Sixers couldn't cut him without adding someone else.
A few more notes on NBA roster sizes:
Note: This is a Hoops Rumors Glossary entry. Our glossary posts will explain specific rules relating to trades, free agency, or other aspects of the NBA's Collective Bargaining Agreement. Larry Coon's Salary Cap FAQ was used in the creation of this post.