“Gay” is a term that those with homosexual inclinations prefer to be called. “Lesbian” is a term that women with homosexual inclinations prefer to be called. Homosexual inclinations are those by which people desire to have sexual relations with members of their own sex.
How could homosexuality, in itself, be a sin? Sins are acts that are contrary to what God expects of us. An inclination is not an act.
Thinking, in itself, is not a sin. For anyone, regardless of sexual inclination, to recognize someone else as sexually attractive is not a sin. On the other hand, to deliberately allow oneself to be temped by particular thoughts, sexual or otherwise, can be an occasion of sin or it can actually be sinful in itself.
Scripture condemns homosexual activity—not the inclination itself.
Fr. Vincent Serpa, O.P.