infidelity
n. C / Un. the act of being unfaithful to a romantic partner, such as a husband or wife. It usually means having a secret relationship with someone else.
n. the action or state of being unfaithful to a spouse or other sexual partner. Often carries a moral or legal connotation in discussions of marriage and divorce.
The couple went to therapy after his infidelity was discovered.
Many marriages struggle to survive the breach of trust caused by a single instance of infidelity.
The novel explores the emotional fallout of infidelity, focusing less on the act itself and more on the slow erosion of intimacy that precedes the betrayal.
From Middle English infidelite, from Middle French infidelité (modern French infidélité) and its etymon Latin īnfidēlitās. Equivalent to infidel + -ity.
Uncountable when referring to the general concept; countable when referring to specific instances or acts.