One who forfeits; a person who loses or gives up something, especially as a penalty or consequence.
From 'forfeit' + '-er' (suffix creating agent nouns, those who perform the action). This noun form developed in legal contexts to name those who lost their property or rights through wrongdoing or breach of contract.
A 'forfeiter' is technically anyone who loses something as a penalty, but the word is rarely used outside legal documents—modern English just says 'the person who forfeited.' Language naturally prefers active descriptions ('they forfeited') over agent nouns for common concepts.
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