Definition
Consensus in blockchain is the mechanism by which a distributed set of nodes agrees on the current state of the ledger and the validity of new data, such as blocks or transactions. It specifies the rules, conditions, and decision criteria that determine when a proposed state is accepted as the canonical chain, despite network latency, faults, or adversarial behavior.
In Simple Terms
Consensus is the rule system that helps all the computers in a blockchain network agree on which transactions are valid and what the official version of the ledger is. It tells the network when to treat a new block as accepted so that everyone stays synchronized.
Context and Usage
The term consensus is central in discussions about blockchain security, decentralization, and performance. It appears in protocol specifications, research papers, and network design debates when describing how nodes coordinate and agree on blocks. Different consensus families and algorithms are evaluated in terms of safety, liveness, and assumptions about network conditions and participant behavior.