Account Model
An accounting design where the network stores a running balance for each account, like rows in a ledger.
Ethereum and many chains that followed it keep an account object holding a balance, a transaction counter called a nonce, and for contract accounts the code and its storage. A transfer simply debits one account and credits another, and a contract call updates whatever the contract's code says, which makes long-lived shared programs straightforward to write. The nonce is required so that a signed transaction cannot be replayed a second time, and it forces a sender's transactions to execute in order. The trade-off is that every account and contract permanently occupies space in state, so the account model grows the data that every node must keep.
実際の運用
An Ethereum transaction with a nonce lower than the account's current nonce is rejected outright, which is what prevents an old signed transfer from being replayed.
よくある誤解
The account model does not make transactions reversible or supervised; an account is a ledger entry keyed by an address, with no operator able to adjust it.