unfaithfulness (n.)

• adultery
• affair
• amour
• barratry
• cuckoldry
• dereliction
• disaffection
• disloyalty
• entanglement
• faithlessness
• falseness
• falsity
• fickleness
• flirtation
• inconstancy
• infidelity
• intrigue
• liaison
• perfidiousness
• perfidy
• romance
• triangle