faithlessness

1. He divorced his wife on the grounds of her faithlessness.
   他与妻子离婚，理由是她对他不忠。
2. They throw all the blame on the faithlessness of their partner.
   他们把所有过错都怪罪於他们同伴的不可信赖。

noun

1. unfaithfulness by virtue of being unreliable or treacherous

   Synonym:    falsenessficklenessinconstancy