Change

In cryptocurrency, "change" refers to the leftover amount of cryptocurrency that remains in a transaction after the desired amount has been sent to the recipient. When you make a transaction and the amount you're sending is less than the total value of the inputs used in the transaction, the excess amount is considered change. This change is usually returned to one of your own addresses as an output of the transaction.

Example:

Let's say you want to send 0.5 Bitcoin (BTC) to a friend, but you only have a 1 BTC bill. In this case, you would create a transaction where you send 0.5 BTC to your friend's address and 0.5 BTC back to yourself as change. The change output ensures that the entire value of the 1 BTC bill is used, and the remainder is returned to you.

Cases:

1. Alice wants to send 0.2 Ether (ETH) to Bob, but she only has a 0.5 ETH bill. She creates a transaction where she sends 0.2 ETH to Bob and 0.3 ETH back to herself as change.
2. John purchases a product worth 0.01 Bitcoin (BTC) using a 0.05 BTC bill. The transaction sends 0.01 BTC to the merchant and 0.04 BTC back to John as change.
3. Sarah wants to make a donation of 5 Litecoin (LTC) but only has a 10 LTC bill. She sends 5 LTC to the charity and 5 LTC back to herself as change.

In each case, the change ensures that the entire value of the input is utilized, with the remaining amount returned to the sender's control.