English Reference
noun

infidelity

n.
US /ˌɪnfɪˈdɛɫɪti/ UK /ˌɪnfɪdˈɛlɪti/ in·fi·deli·ty UK spelling infidelities

  1. 01 C2 Proficiency Formal

    a failure to be loyal to a promise, a duty, or a set of beliefs.

    a breach of trust or a failure to remain loyal to a moral or professional obligation.

    Simple

    The general was accused of infidelity to the crown.

    In context

    The philosopher argued that intellectual infidelity — the betrayal of one's own logic for personal gain — was the greatest vice of the age.

    disloyaltytreacherybetrayal
  2. 02 C2 Proficiency ArchaicFormal Religion

    a lack of belief in a particular religion or in God.

    the state of having no religious belief or of rejecting a specific faith.

    Simple

    In the past, people were sometimes punished for their religious infidelity.

    In context

    The medieval text contains a lengthy polemic against the perceived infidelity of neighboring tribes who refused to convert.

    Teacher's tip

    This sense is rarely used in modern conversation; 'atheism' or 'secularism' is preferred unless discussing historical religious conflicts.

    pietydevoutness

Parton’s lyrics contrast the man’s thin lies about “going on fishing trips” with her suspicion of his infidelities.

The Conversation· 28 Aug 2026

A pop star writes a song accusing her husband of infidelity.

The Guardian· 28 Aug 2026

From Middle English infidelite, from Middle French infidelité (modern French infidélité) and its etymon Latin īnfidēlitās. Equivalent to infidel + -ity.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin īnfidēlitās
Level C1 · Advanced
Frequency Frequent
Updated