Halving is a 50% reduction of mining block rewards for a particular cryptocurrency. These are scheduled to happen every four years for Bitcoin. Miners receive bitcoin for each transaction they approve on the bitcoin blockchain. A specific quantity of bitcoin is released into circulation as each block on the blockchain is filled with transactions. However, only a finite amount of bitcoin will be will only ever be a finite amount of bitcoin created—21 million. The number of bitcoin miners receives for filling a block in half when it is finished to ensure that this cap is maintained. We call this halving. For the record, all 21 million bitcoins will be in use by the year 2140.