DEAR ABBY: I am a newly married person and I don't know what to call my mother-in-law. I can't address her as "Mrs. Smith" as I did before I was married, and addressing her as "Molly" would seem presumptuous and lacking in respect.

She has asked me to call her "Mother," but my own mother is still living, and I would have great difficulty calling anyone except my own mother "Mother."Can you help me? - STUMPED

DEAR STUMPED: I think I can provide a solution to your problem, and to all others who share it, by publishing a letter from a reader who wrote to me some time ago:

DEAR ABBY: I would like to help all young marrieds who find it difficult to address their mothers-in-law as "Mother."

When I made my first visit to the doctor's office after the birth of my first child, the nurse motioned to me and said, "Mother, you are next."

I knew she wasn't addressing me as HER mother. Suddenly I realized that she addressed all of us with children as "Mother."

Immediately my vision was broadened, and I came to understand that "Mother" applied to all women with children. That was the moment I was lifted out of the narrow rut of thinking that the title belonged only to my own mother.

I soon put this knowledge to practice. When I wanted to attract the attention of friends, neighbors or even strangers, I would say, "Mother, watch your little one!"

You'd be surprised how quickly they reacted, having been reminded that they were mothers. The title is rightly theirs, and it never interfered with the special meaning it held for my own dear mother.

If we would all use the term freely, the next generation would learn from our example and thus alleviate a sticky problem. - BIRMINGHAM

DEAR ABBY: What is the significance of wearing a single carnation on Mother's Day? - MIMI

DEAR MIMI: A red carnation is worn to signify that one's mother is living. And a white carnation signifies that one's mother is deceased.

There should also be an identifying flower worn by those whose mothers chose motherhood by raising a foster child, adopting a child or raising a stepchild.

And a special place in heaven awaits those mothers who chose an "imperfect" child, knowing that physically or mentally handicapped children require not only special needs, but also a superabundance of love, understanding and patience.

"How to Write Letters for All Occasions" provides sample letters of congratulations, thank-yous, condolences, resumes and business letters - even how to write a love letter. It also includes how to properly address the clergy, government officials, dignitaries, widows and others. 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, Letter Booklet, P.O. Box 447, Mount Morris, IL 61054. (Postage is included.)