What does unfaithful mean?
Unfaithful means disloyal or untrustworthy, especially when someone breaks a promise, betrays a partner, or fails to meet a duty to another person or institution. Its most familiar use concerns romantic relationships, where it can imply sexual betrayal, although the word also describes wider forms of treachery, such as an employee who steals from an employer or a member who betrays an organization. Unfaithful can additionally mean inaccurate or insufficiently faithful to an original, as in an unfaithful translation or summary. The adjective is generally considered more severe and personal than simply inaccurate. Its negative force comes from combining the ordinary sense of keeping faith with the idea of actively breaking that trust. Unfaithful is especially useful when the failure is not merely accidental but involves a violated commitment, loyalty, or fidelity.
adjectiveDisloyal or untrustworthy, especially toward a partner, friend, organization, or set of beliefs. It can also mean inaccurate or not faithful to an original, such as in a translation or representation.
- Not loyal or faithful to a person, commitment, or belief; disloyal or betraying of trust.
- Not accurate or faithful to an original; inaccurate, altered, or unfaithful in reproduction or representation.
"She left her unfaithful husband and began rebuilding her life."
"The unfaithful employee copied confidential files before leaving the company."
"The guide's unfaithful translation softened several of the original author's objections."
Unfaithful can describe a person betraying trust—or a translation quietly changing the original.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does unfaithful come from?
The word was formed in English by adding the prefix un-, meaning “not,” to faithful. The prefix descends from Old English, while faithful belongs to the English vocabulary derived from older Germanic forms associated with faith, trust, and loyalty. Related Latin words such as fidelity and fiduciary reflect the broader family of words connected with trust and faithfulness.
Related word forms
How unfaithful is actually used
In its dominant interpersonal sense, the word is strongly negative and commonly concerns romantic partners, friends, employees, or political allegiance. When applied to a translation, account, or representation, it describes a failure to preserve the original meaning accurately.
Easily confused with unfaithful
Faithless describes a lack of faith, trust, or loyalty, whereas unfaithful more directly describes betrayal of a specific relationship, duty, or standard.