Modifies a noun

• affair: A husband who was racked with remorse over an extramarital affair killed himself by lying down in front of a train.

• sex: However underage sex and extramarital sex are both thought to be mostly or always wrong by a large majority.

• relationship: One survey pointed out that nearly 70 percent of all married men under the age of forty expect to have an extramarital relationship.

• fling: It's all stirred up by Tomiko, who wants an extramarital fling with Tsutomu herself.

• activity: Mr. Miller is trying to pry the matter back open by alleging that his client's ex-wife fraudulently concealed her extramarital activity.