Family Therapy: A therapy session that includes more than one member of the same nuclear family. See related article on Choosing a Therapist

Fellatio: When oral sex is performed on a male also known as a blow job. (See Oral Sex)

Female Condom: A condom that fits inside the vagina.

Finances: The management of money to pay expenses and adding to savings. See related article Teen Finance

Flaccid: The relaxed state of a penis.

Flashbacks: The re-experiencing, after discontinuing use, of the effects of a hallucinogen such as LSD. 

Foreskin: The loose skin covering the end of a penis in uncircumcised males.

French Kissing: An open mouth kiss where tongues touch or is put in the other person's mouth.

Frottage: Rubbing two bodies together for sexual pleasure also known as dry-humping.