Infidelity in a marriage often leads to a complete breakdown of trust.

infidelity 由前缀 in-（表示"否定"）和词根 fidelity（忠诚）组成。fidelity 来自拉丁语 fidelis（忠诚的），所以 infidelity 字面意思是"不忠诚"，特指"（婚姻中的）不忠行为"。