# unfaithful

/ənˈfeɪθfəɫ/ (US) · /ʌnfˈeɪθfəl/ (UK) · CEFR B2 · Adjective

Source: https://englishreference.com/word/unfaithful
Updated: 2026-05-09

## Definition

having a sexual or romantic relationship with someone who is not your husband, wife, or partner. It can also mean not being loyal to a person, group, or set of beliefs.

For teachers: engaging in sexual or romantic relations with a person other than one's established partner; failing to remain loyal to a person, organization, or principle.

## Examples

- He was unfaithful to his wife for many years.
- The politician lost the support of his party after he was found to be unfaithful to their core values.
- The novel explores the psychological toll of being unfaithful, focusing on the protagonist's internal struggle between his personal desires and his commitment to his family.

## Usage notes

- Typically followed by the preposition 'to' when identifying the person or entity being betrayed.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.