"BEST FRIENDS" is a classification of human social relationships that Miss Manners has long tried in vain to discourage small children from declaring. Nothing good can come of a partnership in which both people recognize the obligations and neither the duties.

Your best friend, under elementary-school conditions, is someone who is always available to you but not a nuisance when you want to play with someone else. A best friend rejoices in your triumphs but does not have successes that overshadow them. A best friend commiserates with you, but does not bore you with recitals of woe. A best friend confers distinction on you but cooperates in seeming disassociated from you when there is only embarrassment to be shared. A best friend tells you all the gossip about everyone, but is never tempted to repeat your confidences.

Miss Manners knows of several marriages that were established with these expectations.

"Why," she keeps asking little children, "do you have to be 'best friends'? Why can't you just be friends? That way you can have other friends, too, and no one is hurt."

"Because," they always say, "it's different." Miss Manners tries to remember not to argue with little children.

She will turn her attention, instead, to grown-ups, and lecture them on how to be "best friends." There is such a thing as "best friendship" between grown-ups, and even occasionally grown-ups of opposite genders. And yes, Miss Manners will permit you to have your opposite gender "best friend" stand up for you, as they say, at your wedding.

But what most grown-ups mean when they speak of such best friends is not true "best friendship." Better, perhaps, but not best. When a gentleman says his wife is his best friend, or a lady says that a gentleman and she are nothing but the best of friends, they are talking about something else.

Your best friend is someone who delights you by confessing to having fallen happily in love with someone you haven't yet met. See the difference?

The duties of grown-up "best friends" are similar to what children expect, but must be mutual. The chronically cheerful and the chronically morose can seldom sustain a best friendship, with one always listening to the other's rejoicings and the other only hearing complaints.

Specifically, a best friend must:

Admire unreservedly your fiance, new baby and newly purchased house.

Entertain a warm respect for your parents, spouse, grown-up children and employer, but maintain a bias in your favor when a conflict exists.

Tell you when your clothes are seriously awry if you are in a position to fix them, and deny that there was ever anything the matter if you are not.

Tie you to a tree when you announce that you are going to tell your boss what you think of him.

Work at your parties, filling silences and flattering wallflowers, instead of having a good time.

Tell you first of any major steps he or she is taking, but allow you to go around announcing yours without getting in with the story first.

Treat your misfortunes as serious instances of bad luck, not the result of character flaws.

Treat your successes as the just rewards of character and ability.

Enjoy your successes more than your misfortunes.

Consider that any addition to your life that seems to please you is wonderful--including a new friend to shoot marbles with.

MISS MANNERS RESPONDS

Q. I would like to hear your comments on the situation when two lovers have widely differing incomes. We are both without dependents, and habitually pay our own ways. However, my income affords me a lot more leeway in my choices than hers does.

For now, the immediate issues focus on entertainment and air fares, since I am on job assignment far from home. The city I am staying in is much more interesting and fun to visit than our home city. Under what circumstances is it proper for me to pay her fare to come visit me here?

In future, as we think of living together, the question will again arise, since I can afford to buy a house, and she cannot. She doesn't want to be dependent and renting from me, and my tax situation demands home ownership. Is there a good way to deal with this? So far, my response has been to encourage her in seeking a better-paying career.

Does it matter to your answer that we're both women?

A. Yes, it matters, because Miss Manners was going to tell you to get married, pool your incomes without counting who contributed what, and let Miss Manners get back to her nap. Now she feels she has to answer your question, instead.

It is probably just as well, because all sorts of couples seem to have problems with shared finances these days, and Miss Manners had better face the issue. Let us see if she can work out a solution that will allow lovers to maintain their financial independence without succumbing to the kind of you-ordered-a-drink-and-I-didn't arguments that can kill any social relationship.

The house is easy. Ownership does not have to be 50-50. You can have 80 percent equity in it, for example, and she 20. It would seem fair to Miss Manners to then decide that you will have the right to buy her out if you decide to split up.

The important thing to remember is that sharing living in a house is something quite different from sharing the cost. That you paid more is irrelevant when it comes to choosing bedrooms or closets, entertaining friends, or whatever. Marriages in which the wage-earner claimed special privileges are what drove people to exact accounting in the first place.

As for entertainment, you can take turns, with the richer person providing more expensive meals or theater tickets, and the fact that the other person chooses less expensive places being graciously ignored. If you find it advantageous to have her come to your city, make her an occasional present of tickets, and explain that taking them is a favor to you, too.

Encouraging her to change careers is silly; you might just as well take a salary cut yourself, if you think love is only possible between exact financial equals. If money can't buy love, it seems ungracious for love to haggle over money.

Q. I own a pair of beautiful gold antique bracelets, valued at $600 each. I planned to give one to my soon-to-be daughter-in-law as a personal wedding gift. Inside the bracelets is a date, 1880, and initials of a long-gone relative. My question, considering that the initials do not match the bride's, is whether it would be proper to give this gift. Also, if you say it would be fitting and proper, would it be tacky of me to suggest to her that the bracelet is of some value, and not just junk jewelry?

A. There is no more charming present a bride can receive from her new family than something that has been treasured in that family for many years--unless it is a $600 gold bracelet that has been treasured, etc. You are quite right that your prospective daughter-in-law must understand what it is that she is getting. The non-tacky way of doing this is with a small presentation speech that goes, "My dear, I hope you don't think this too old-fashioned to wear. It was given to my great-great Aunt Flora when she was a bride, and I hope some day that you will give it to your son's wife, if he should be so fortunate as to have as lovely a bride as my son chose."

If she doesn't understand the value after that, Miss Manners must advise you to suggest that your son find himself a bride who is a little quicker mentally.