Unmarried means not married. An unmarried couple, unmarried mother, remained unmarried.
It is the neutral term, where single covers not being in a relationship at all and the two are often confused on forms. In British law, unmarried couples have no automatic rights over each other's property however long they live together — the common-law marriage is a myth, and it is one of the more consequential things people wrongly believe.
1adjectiveunmarriedNot married.
“Her aunt remained unmarried and lived alone all her life.”
unmarried is a marital status.
Also accepted in games: unwed
Middle English
maried
English
married
English, today
unmarried
From un- + married. married comes from Middle English maried, imaried, mariet, past participle of Middle English marien (“to marry”), equivalent to marry + -ed.
Etymology from Wiktionary, CC BY-SA