Tom's wife had an extramarital affair.

Tom had an extramarital affair.

Sami had an extramarital affair.

Are you involved in an extramarital affair?" "That's ridiculous."

I would be surprised if Tom had never had any extramarital affairs.

Sami's birth resulted from an extramarital affair.

He has never had extramarital relations.

Tom had been having a secret extramarital affair, alternating between two women for the past six months.