DEAR ABBY: I wrote to you 26 years ago about my stepfather and my brother. Now I'm writing to you about my son -- I'll call him Lewis. He's my only child and a junior in high school. His father and I have been divorced since Lewis was 2 years old, and he has lived with his father, who is principal of a large high school, for several years.

Lewis is intelligent, but in spite of that, he struggles to maintain grades high enough to keep himself eligible to play sports. I could accept that, since his father was a late bloomer, but I have trouble with his lying. Lewis constantly cons his dad, me, his teachers and his friends.

Since I live 2 1/2 hours away from my son, I cannot be a daily influence. We talk frequently on the phone; however, we don't see each other often. I used to enjoy our telephone conversations, but about three years ago, I realized he was lying to me. It's getting worse -- to the point that I cannot believe anything he says, and that's breaking my heart. Of course, Lewis denies telling lies.

I want to help him, but I don't know how. Abby, this seems to be a family trait. His father, his grandmother and his aunt are liars, but they won't admit it -- they just keep on lying.

What will the future hold for Lewis if he continues to lie? Will he grow out of it? How can I help him? Does he need psychiatric help? -- OHIO MOTHER

DEAR MOTHER: Evidently lying brings more benefits to your son than telling the truth. Lying is habit-forming. Furthermore, a liar continues to lie until he actually believes his own lies. There may also be a psychological reason for the lying.

Obviously, his future will be in jeopardy if he continues to lie. "Outsiders" will not be as forgiving as his family, and he will surely lose friends (and probably jobs) when he gets caught in his lies.

Will he grow out of it? Not unless he is consistently confronted by his family when he lies, and gets professional counseling. Insist that he get into a program of counseling, and when you catch him in a lie, point it out and insist that he tell you the truth.

P.S. His poor performance in school is another indication that he could benefit from counseling.

DEAR ABBY: I am 22 and recently broke up with a longtime boyfriend. I have been reintroduced to someone with whom I went to high school. However, I didn't know him well back then.

Abby, this man says all the right things, but I'm not sure how to tell the difference between sincerity and the "lines" men use these days. Do all men say the things a girl wants to hear just to get what they want? Is it possible to tell the difference between sincerity and these "lines"? Are there any telltale signs I should watch for? -- LEERY IN VIRGINIA

DEAR LEERY: The best test of sincerity is time. Watch for inconsistencies and observe whether they always result in him getting what HE wants, rather than in what makes YOU happy.

If he's still saying "all the right things" after a couple of months, the odds are that he's sincere and you are a lucky lady.

What teens need to know about sex, drugs, AIDS, and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-sized, 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. 61054-0447. (Postage is included.)

DEAR READERS: Yesterday I published a letter from the grandparents of a 19-year-old woman who was brutally murdered by a young man with whom she had lived for four months. Her grieving family asked if I would reprint the column that outlined the traits of a potential batterer. In her memory, here it is. It was adapted from "Signs to Look for in a Battering Personality," with permission from the Project for Victims of Family Violence, Fayetteville, Ark.

15 REASONS TO LEAVE YOUR LOVER,

WARNING SIGNS OF AN ABUSIVE PERSONALITY

Something's just not right in your relationship, and you can't put your finger on it. So here's some help. If your mate is displaying a combination of these behaviors, then you may have a potential batterer on your hands.

1. A PUSH FOR QUICK INVOLVEMENT: Comes on very strong, claiming, "I've never felt loved like this by anyone." An abuser pressures the woman for an exclusive commitment almost immediately.

2. JEALOUSY: Excessively possessive; calls constantly or visits unexpectedly; prevents you from going to work because "you might meet someone"; checks the mileage on your car.

3. CONTROLLING: Interrogates you intensely (especially if you're late) about whom you talked to, and where you were; keeps all the money; insists you ask permission to go anywhere or do anything.

4. UNREALISTIC EXPECTATIONS: Expects you to be the perfect woman and meet his every need.

5. ISOLATION: Tries to cut you off from family and friends; accuses people who are your supporters of "causing trouble"; the abuser may deprive you of a phone or car or try to prevent you from holding a job.

6. BLAMES OTHERS FOR PROBLEMS AND MISTAKES: The boss, you -- it's always someone else's fault if anything goes wrong.

7. MAKES EVERYONE ELSE RESPONSIBLE FOR HIS FEELINGS: The abuser says, "You make me angry" instead of, "I am angry" or, "You're hurting me by not doing what I tell you." Less obvious is the claim: "You make me happy."

8. HYPERSENSITIVITY: Is easily insulted, claiming that his feelings are hurt when he is really mad. He'll rant about the injustice of things that are just part of life.

3. CRUELTY TO ANIMALS AND TO CHILDREN: Kills or punishes animals brutally. Also may expect children to do things that are far beyond their ability (whips a 2-year-old for wetting a diaper) or may tease them until they cry. Sixty-five percent of abusers who beat their partner will also abuse children.

10. "PLAYFUL" USE OF FORCE DURING SEX: Enjoys throwing you down or holding you down against your will during sex; says he finds the idea of rape exciting.

11. VERBAL ABUSE: Constantly criticizes you, or says blatantly cruel, hurtful things; degrades, curses, calls you ugly names. This may also involve sleep deprivation, waking you up with relentless verbal abuse.

12. RIGID SEX ROLES: Expects you to serve, obey and remain at home.

13. SUDDEN MOOD SWINGS: Switches from sweetly loving to explosively violent in a matter of minutes.

14. PAST BATTERING: Admits hitting women in the past, but says they made him do it or the situation brought it on.

15. THREATS OF VIOLENCE: Makes statements like, "I'll break your neck" or "I'll kill you," and then dismisses them with, "Everybody talks that way" or "I didn't really mean it." If he has come this far, it is time to get help, or get out.

Good advice for everyone -- teens to seniors -- is in "The Anger in All of Us and How to Deal With It." To order, send a business-sized, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, Anger Booklet, P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)

DEAR ABBY: "Irritated in Ojai, Calif." was bothered by the fact that her husband has kept love letters from a previous girlfriend for more than 12 years and through three moves.

I've kept a previous boyfriend's love letters for 23 years and through seven moves. My husband has never asked me to dispose of them, and I wouldn't toss them even if he asked me to. These letters, along with other assorted keepsakes, help me define who I am now, based in part on who I've been in the past. The letters are nothing more than a record of a girl who was able to love and be loved -- an important concept to someone who felt unloved by her family.

In my mind, they affirm my ability to have a loving relationship with my husband. Please encourage "Irritated" not to stop at simply telling her husband how she feels about the letters (and then waiting for him to "toss them out"). Tell her to take the time to explore with him the reason he has kept those letters. It may be an eye-opening, soul-searching experience for them both! -- DARLENE IN REDONDO BEACH, CALIF.

DEAR DARLENE: While it may be a "soul-searching experience" for some, it could be something else for others.

People keep love letters for a variety of reasons, but it's a pretty good bet that there is an underlying sentimental reason. This is the private business of the keeper -- why must it be "explained"?

DEAR ABBY: I seldom miss your column in our local newspaper. Our family often discusses and learns from the letters you publish. You have helped us many times, as you have so many of your readers.

It was only after the death of my granddaughter that I saw the letter you printed from the 25-year-old woman thanking you for saving her life by printing the warning signs of an abusive partner. After seeing your column and recognizing that her boyfriend fit every warning you mentioned, she left him and started a new life.

How I wish our beautiful 19-year-old granddaughter had seen that list. She had been living with a young man for four months. Although her family didn't approve of him and had tried to dissuade her from living with him, they made an effort to accept him and welcome him into the family so they wouldn't lose their daughter.

After a particularly nasty quarrel, my granddaughter separated from the young man and returned to her family. A week after she left him, he brutally murdered her. Although she had been close to her parents (and all the family), she had never once confided to anyone the abusive relationship she was in. Her parents are devastated. Their lives have changed forever.

Our family would like to be able to help other young women in these circumstances, but we don't know how to get started, Abby. Do you have any suggestions? And would you please print the warning signs of an abuser again? -- TOO LATE IN TEXAS

DEAR TOO LATE: Please accept my deepest sympathy on the tragic loss of your granddaughter. I'm sure there are many ways in which you could help other young women in abusive relationships. The most obvious would be to explore what help is available to battered and homeless women in your city and find out what their immediate needs are -- shelter, clothing, funds to tide them over. You might also consider contacting victims' rights groups.

For anyone who might have missed it, I will publish the warning signs of an abusive partner tomorrow. Space limitations prevent me from doing it today.

Abby shares more of her favorite, easy-to-prepare recipes. To order, send a business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, More Favorite Recipes, P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)