What Is ‘Finality’ in a Blockchain Context like Ethereum?

Finality refers to the guarantee that once a transaction is included in the blockchain, it cannot be reverted, altered, or canceled. In Proof-of-Stake systems, finality is achieved when a supermajority of validators attests to a block, making the cost of reversing the transaction economically prohibitive.

This is a critical security feature that ensures trust in the transaction history.