Infidelity
Noun, な adjective, and の adjective
ふてい
妻が不貞をはたらいたので、離婚しました。
My wife was unfaithful so we got divorced.
When you do not have chastity, it's probably because you were unfaithful to your promise to whoever you told you'd stay chaste to.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.