In law, void means of no legal effect. An action, document, or transaction which is void is of no legal effect whatsoever: an absolute nullity—the law treats it as if it had never existed or happened. The term void ab initio, which means "to be treated as invalid from the outset", comes from adding the Latin phrase ab initio (from the beginning) as a qualifier. For example, in many jurisdictions where a person signs a contract under duress, that contract is treated as being void ab initio. The frequent combination "null and void" is a legal doublet.
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The term is frequently used in contradistinction to the term "voidable" and "unenforceable".