Halving

1 [definition]
A decrease in block rewards by 50% at a set time determined by block height
2 [mining]
To control the rate of new tokens into the network, many blockchains reduce the mining rewards at set scheduled block heights. This event is known as a halving. At this time, the reward for mining is cut in half, which also means the rate of new tokens being introduced into the system is reduced by half.

These events historically lead to increased scarcity, and price increases.