In a choir or theater, the stalls are the block of seats at the front of the main floor directly before the stage. In the United States these seats are also called the orchestra because that is the location where musicians sit during performances that require live music to accompany the performance. These seats are close to the stage, but may require the people sitting in them to look up at an awkward angle to see the performance.
Many small enclosures are referred to as stalls. These include the small buildings used in many marketplaces to hold goods, and also partitioned spaces in interior locations. Market stalls commonly consist of low walls with an open counter to the front and a roof that can either be solid or made of canvas. Interior stalls are found in bathrooms, such as toilet stalls in public restrooms or the shower stall in many home bathrooms. They can also be found in barns, where a stall is a small space divided by walls and holding one or few animals.
An engine stalls when it stops in an unexpected or unwanted manner. Manual transmission vehicles can easily be stalled by improper use of the clutch and gears, and stalls can also be signs of tainted fuel, poor maintenance or a larger failure about to happen. Related to engine stalls are compressor stalls, when the fans in a turbojet engine are unable to push properly on the air going through the engine and the engine stops producing thrust.
Surface stalls are most commonly encountered in flight, when an aerodynamic surface loses its effectiveness. Airfoils work by forcing air to travel longer distances over one side than over the other. The longer distance traveled by the air reduces the air pressure on that side of the foil, and the difference in pressure between the two sides creates a lift in the direction of the longer side. If the foil is tilted up so that the oncoming air presses more heavily on the flat surface, the foil becomes less effective. If it is tilted at a sufficiently high angle there is no difference between the air pressures on either side of the foil, and the foil stops producing lift. This phenomenon can easily be observed by watching a paper airplane turn its nose up, stop in air, then begin to fall and pick up speed again.
Airfoils are not the only surfaces that can stall. Hydrofoils such as the rudders and keels used by boats can also lose effectiveness if placed at the wrong angle to the oncoming fluid. Boat sails are also a form of airfoil and can stall, or luff, if placed at the wrong angle to the wind.
Stalls, or stalling, also refers to the process of intentionally slowing play when one player has the lead. This is most commonly found in timed games such as basketball, where the team with the lead will attempt to use up the time as much as possible to reduce the other team's ability to mount a comeback. Stalling is also a tactic used in card games, intentionally taking up time either to end the clock or to give time for a player or his partner to think about his next move. Stalls in games have been limited by adding a shot clock or play clock to force teams to take action.