infidelity
/ˌɪnfɪˈdelətɪ/noun
(pl. -ies) ［mass noun］
1
- the action or state of being unfaithful to a spouse or other sexual partner（对配偶或性伙伴的）不忠行为; 不忠：
her infidelity continued after her marriage
她婚后仍有不忠行为
count noun I ought not to have tolerated his infidelities.我当初不应容忍他的不忠行为。
2
- disbelief in a particular religion, especially Christianity不信奉宗教（尤指基督教）。
词源
late Middle English （in the senses 'lack of faith' and 'disloyalty'）: from Old French infidelite or Latin infidelitas, from infidelis 'not faithful' （see INFIDEL）.