DEAR ABBY: What, exactly, is a person's "IQ," and how is it determined? -- A STUDENT IN GREEN BAY, WIS.

DEAR STUDENT: "IQ" stands for intelligence quotient, and it is determined by assigning a number to the level of skills attained on a standardized test. This number, sometimes called the "mental age" or M.A., is divided by the chronological age (C.A.) and then multiplied by 100. The total reflects one's comparison to a standardized group of this age.

For educational purposes, the IQ scores are categorized as follows: 125 to 140 or higher -- gifted; 115 or higher -- highly intelligent; 100 -- average.

Educable: An IQ of 50 to 75. One who can be educated academically to the level of an average child of 9 to 11 years of age, can socially adjust to family and home, and can occupationally support themselves totally or partly.

Trainable: An IQ of 25 to 50. One who can be trained to perform self-care skills such as dressing, feeding and toilette, can socially adjust to the home and neighborhood, and can gain some degree of ability such as routine tasks within the home or in a sheltered environment under supervision.

A person with an IQ under 25 usually requires nursing care, and is considered totally dependent.

DEAR ABBY: My grown daughter is my best friend. She has given me some of life's greatest joys -- and sorrows. She is supportive, loving and generous, but she also "steals" from me. In spite of my arguments, threats and pleas, she fraudulently charges on my credit cards and is dishonest when confronted with her wrongs.

I am a widow on a fixed income and cannot continue to see my savings depleted to pay her bills. I've considered moving far away to protect myself, but am dependent on her for the good times, love and friendship we share, plus she is the mother of the grandson who is the light of my life.

Recently she began counseling to help cure her compulsive spending, and deal with her anxiety and guilt.

I do not want to jeopardize her job or her marriage, but I am desperate to find a way to help her and protect my financial security. Please help me. -- GOING DOWN THE DRAIN

DEAR GOING: Notify the stores where you have charge accounts that no one other than you may use your charge account. Then tell your daughter that in order to protect yourself from bankruptcy -- and herself from humiliation and trouble with the law -- she must not attempt to charge anything on your accounts.

Since your daughter is in counseling to overcome her compulsive spending, at least she's trying. Let's hope she succeeds.

Want your phone to ring? Get Abby's booklet, "How to Be Popular" -- for people of all ages. 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, Popularity Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.

DEAR ABBY: I am a 25-year-old white male who, until recently, thought I had everything going for me. I had a wonderful girlfriend, a good-paying job, a nice apartment and a nice car. Then I began to use intravenous drugs and before I knew it, a year had blurred by. Today I have lost everything, everything!

I began to burglarize homes for money to buy drugs. I have lost all that was dear to me and am currently serving time in prison for burglary. While incarcerated, I lost my father to cancer, and the hardest thing I've ever had to do was walk down that church aisle to pay my last respects to my father -- escorted by two guards and in shackles and handcuffs! Dad was always there for me, but I couldn't be there for him in his last days.

Also, I found out that I have AIDS from using someone else's needles, and I don't know how much time I have left.

I want to run to every teen-ager, grab them and scream at them, "NEVER, NEVER TOUCH DRUGS!"

If I survive my incarceration (2 to 4 years), I want to tour schools and try to teach some of these kids before it's too late by telling them what I have learned. I can also tell them what they will miss as I'm finding out now: I can't have a normal, healthy relationship with someone I care for, for fear of infecting her. I will never know the joy of fatherhood because the AIDS virus could be transmitted to my child. There is so much in life I will miss -- and all because of drugs. -- TOO LATE FOR ME

DEAR TOO LATE: If you never get to "tour schools," you will have performed a valuable service by writing this letter. As you can see, I have printed your letter in full. God bless you, young man.

DEAR ABBY: Please tell me if I am right or wrong. My daughter-in-law's brother, "Bob," was married last week, and I was invited to the wedding. It was a big social event, and one of the most beautiful weddings ever held in our cathedral.

My daughter, "Lisa," was not invited, and now she's mad at me because I went. She thinks I should not have gone because she wasn't invited. Abby, there is no reason why Lisa should have been invited -- she's not related to Bob, and I am related only through marriage. Also, she's never even met the bride. Do you think she's justified in being angry and insulted over this? Now she hates me because I attended the wedding.

Lisa is in her 50s and I am in my 80s. -- HURT IN BROOKLYN

DEAR HURT: Lisa's behavior is childish and unreasonable. Do not permit your daughter to lay a guilt trip on you. If she "hates" you for attending a wedding to which she was not invited -- it's her problem, not yours.

Hot off the press -- Abby's new booklet, "The Anger in All of Us and How to Deal With It." 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, Anger Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)

DEAR ABBY: When I read the letter in your column from the pizza delivery truck driver, I had to write. I also work for a national pizza chain, as an inside person taking telephone orders. (Our goal is to take the order, make the pizza and deliver it within 30 minutes.)

The same parents who allow 3- and 4-year-olds to pay for the pizzas also put them on the phone to order them. I have to keep four adults on hold while trying to decipher the speech of a toddler. Meanwhile, the parents are in the background coaching him or her as to what to order, the address, etc. These parents obviously think this performance is incredibly cute. I have also had 5- and 6-year-olds placing orders as late as 10 and 11 p.m.

Abby, please allow me to point out a few tips for readers who order pizza:

1. Decide what you want to order before you call. We may have people on hold while you are conferring with each other as to what size to order, what toppings, etc.

2. Have the person who knows the address order the pizza.

3. Have your money ready for the driver, since he may have several pizzas to deliver within 30 minutes.

4. Please be on the lookout for your pizza once it's ordered. Turn on a light so your address is visible at night. Have an adult present to pay for the pizza. Also, lock up your Doberman, pit bull terrier, German shepherd, etc.

Thanks, Abby. This is a load off my chest. -- ELAINE IN BALTIMORE

DEAR ELAINE: Grazie for the suggestions.

DEAR ABBY: I was happy to see that piece in your column warning your readers about bringing valuables (jewelry) when they check into a hospital -- even for an overnight stay.

I've been an RN for 12 years and I am still amazed at the stuff people lug into a hospital.

Some come in with loads of suitcases for a week's stay. One woman brought all her diamonds and hid them in a pillowcase -- which almost got thrown in a hamper!

Only last month, a man brought his life's savings of $100,000 in cash! Luckily, an observant employee spotted the stash and called security to place it in the vault for safekeeping.

Elderly and confused patients are most vulnerable. I have seen patients throw wedding rings and hearing aids in the trash cans.

Yes, there are thieves even in hospitals, but it's impossible for us to search every man, woman and child that comes and goes here.

Please print this, Abby. No city, please. -- ROSE, AN R.N.

Everything you'll need to know about planning a wedding can be found in Abby's booklet, "How to Have a Lovely Wedding." 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, Wedding Booklet, P.O. Box 447, Mount Morris, Ill. 61054. (Postage is included.)