En Prison

En Prison is a roulette term used to describe the natural advantage mechanic offered to an even number bet. This mechanic is only triggered when the roulette ball lands on a 0 when playing with a European wheel. There is no such mechanic when playing with an American wheel.

What Happens When the Ball Lands on a 0?

One of several things can happen when a roulette ball lands on a 0:

• If you had placed your bet on an odd number, you will lose your bet.
• If you had placed your bet on an even number, your bet is put “into prison” (En Prison). 

In the second case, the fate of your bet is decided during the next round. If the ball lands on an even number, you will get your bet back in full. If it lands on an odd number, you will lose your bet.

En Prison:

• A roulette mechanic that comes into play when the ball lands on a 0
• Only applies to even-numbered wagers
• Only applies to the European wheel