infidelity (n.)

• adultery
• affair
• agnosticism
• amor
• amour
• apostasy
• atheism
• barratry
• cheating
• cuckoldry
• denial
• dereliction
• disaffection
• disbelief
• discredit
• disloyalty
• entanglement
• faithlessness
• falseness
• falsity
• fickleness
• flirtation
• heresy
• inconstancy
• incredulity
• intrigue
• liaison
• perfidy
• rejection
• romance
• secularism
• traitorousness
• treachery
• triangle
• unbelief
• unfaithfulness