DEAR ABBY: When I was a teenager, you printed a column about how to tell if you are really in love - or if it is just infatuation. My mother clipped it out for me, but I can't seem to find it. I sure could use it just now. - NANCY C. IN SANTA ANA, CALIF.

DEAR NANCY: I'm frequently asked how my mail has changed over the years, but some questions never change, and this is one of them:IS IT LOVE? OR ISN'T IT?

It takes a level head to control a foolish heart.

Can you love someone at first sight? This crazy mixed-up version is better known as INFATUATION at first sight. Infatuation can possibly be the first step toward love, but in itself, it is not love.

Love itself is built on INNER realities. Through experience and a few more infatuations, one acquires a second and better sight. So, mature love should be called "love at second sight."

Mature love means LIKING a person as well as loving. If the most important part of your relationship is physical (making out) and you don't seem to have much to talk about, face it, it's just a physical attraction, and you're really not a very good combination if you're thinking of a lifetime relationship.

How do you know if you're in love? To ask if it IS love indicates doubt. Love is sure.

Don't confuse enduring and lasting love with puppy love. (That's the kind that usually gets you into an emotional doghouse.)

Love is giving, not taking. It wants the best for the one you love.

Love is on the go. It makes you want to charge out into the world and do as well as think big. It doesn't keep you inert, daydreaming and cooped up with only one person.

Love wants to share. To the one you love, you give your thoughts and your dreams. A new happiness comes with sharing them. Mature love is honest and open.

Love doesn't know what time it is. During your teens, you will have had a litter of puppy loves. But as time goes by, and you learn more about the object of your affections . . . and your love seems to grow not weaker but stronger . . . maybe the real moment has come.

DEAR ABBY: I am an airline pilot, which requires me to be away from home two or three nights at a time.

When I am on one of these trips, the crew, both male and female, sometimes dines together. Meanwhile, my wife and six children are at home. I employ a full-time housekeeper to help my wife.

I think it's OK for my wife to go out with her friends at night for shopping, dinner and movies, but I say no when it comes to her going to a disco without me.

She says she enjoys going to discos to dance and listen to the music. I say she can wait until I get home so we can go together. She says she trusts me on my overnights and I should trust her. I do trust her, but why look for trouble?

Do you think I'm being unreasonable? - CORAL SPRINGS, FLA.

DEAR CORAL SPRINGS: No. In my view, a married woman with six children and a husband out of town doesn't belong in a disco listening to music and dancing with strangers.

- What teen-agers teenagers need to know about sex, drugs, AIDS, and getting along with their peers and parents is now in Abby's updated, expanded booklet, "What Every Teen Should Know." To order, send a long, business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, Ill. IL 61054. (Postage is included.)

@ 1990 Universal Press Syndicate