infidelity

From Middle French infidélité, from Latin infidelitas

infidelity (countable and uncountable, plural infidelities)

1. Unfaithfulness in a marriage or an intimate relationship: practice or instance of having a sexual or romantic affair with someone other than one's spouse, without the consent of the spouse.
   • 2013, William G. Staples, Everyday Surveillance: Vigilance and Visibility →ISBN, page 155:

     Your friends tell you rumors about your girlfriend's infidelity or you remember being broken up around the time the baby was conceived.

2. Unfaithfulness in some other moral obligation.
   • 1937, Arnold Oskar Meyer, England in German opinion throughout the centuries, page 6:

     It was disastrous that England's infidelity towards Frederick the Great — which no one, not even a German, condemned more strongly than did William Pitt — had to affect one of the most popular heroes of our national history.

3. Lack of religious belief.
   • Bishop Ward

     The means used to this purpose are partly didactical, and partly protreptical; demonstrating the truth of the gospel, and then urging the professors of those truths to be stedfast^[sic] in the faith, and to beware of infidelity.

• (marital): adultery
• (moral): betrayal
• (religious): faithlessness

• (moral): faithfulness
• (moral): loyalty
• (moral): fidelity

• (religious): infidel

• infidelity on Wikipedia.Wikipedia