A wife recalls "clawing and screaming" at her husband in a jealous fit after he had talked all night with a younger, attractive woman at a party. A divorced man struggles with his obsessive suspicion of his new girlfriend -- always asking himself, "Who is she seeing when she's not seeing me?"

Jealousy, the fear of losing the love of someone to another, is a consuming, debilitating emotion -- rarely admitted to, commonly misunderstood, yet familiar to anyone in a committed relationship.

In any relationship, there is rarely zero jealousy, says Cambridge, Mass., psychiatrist Dr. Lawrence Hartmann. But jealousy is not always bad. The trick is in separating normal jealousy from pathological.

Normal jealousy can be healthy, flattering and reassuring, mental health professionals agree, because it tells someone they are special and of value to the relationship. If a man knows his wife meets another man for lunch on a regular basis, he may feel the need to ask her to keep it platonic. Such a reaction, says Hartmann, is normal and "helpful for two people whose love is important to each other." In this case, the wife can take her husband's wish as a compliment.

But another, more disturbing aspect of normal jealousy, Hartmann says, can come from "actual causes that people can't tolerate, such as love taken away totally by another."

In pathological jealousy, Hartmann explains, there is an exaggerated, or even imagined, cause. Pathological jealousy can eventually suffocate the love it's trying to protect.

"I know men who are fearful of even looking at an attractive woman while driving in the car with their wife," says Dr. Mary Ann Bartusis, a Philadelphia psychiatrist whose expertise is infidelity.

"Eventually, such a man feels so penned in by his wife's nagging suspicion, he begins to think, 'What is it I'm missing out there?' and so he does get involved in an affair."

"Most of us have a wish the infidelity could be blamed on one outside person," says Dr. Hartmann. "But that's a neurotic wish. However, a significant chunk of responsibility can be placed on the pathologically jealous spouse -- and yet not all the blame or responsibility is on one side."

If you are highly suspicious of your spouse who gives you no actual cause for suspicion, it might be you are transferring your anxiety over your desire for an affair. Or, in incidents where the spouse wants the other to appear jealous, "it may be a neurotic need," says Dr. Hartmann, "for proof that 'I do matter to you and you prove it to me by a certain amount of turbulence.' "

What are the roots of such passionate aches of the heart?

Low self-esteem. Most professional observers agree this is a key cause of pathological jealousy. Low self-esteem can be more prevalent at certain times of life, making one vulnerable to the fear of losing a committed relationship.

Low self-esteem is often formed early in life, says Dr. Bartusis, "particularly if you were raised by hypercritical parents who found some small thing wrong with your outfit everytime you dressed up, or criticized your B-plus grade, as not as good as an A." Eventually, says Bartusis, "this negativism subtly brainwashes you so that when you see your spouse looking at someone else, you feel you could never measure up."

*Unrealistic value system. According to Jerilyn Ross, associate director of the Roundhouse Square Psychiatric Center in Alexandria, "People who value highly visible things, such as looks, wealth, intelligence, will find themselves envious and helplessly jealous if such competition should come into their marriage or love affair."

Furthermore, if there is a "discrepancy between how you really are and what you would like to be," Ross says, "you are more likely to be involved in a jealous triangle."

In the triangle of jealousy, says Dr. Bartusis, "it is not always a case of 'the other woman.' " For instance, it can happen in the workplace among three colleagues over a promotion; or in a family where a wife is jealous of her husband and their attractive teen-age daughter; or where a husband is jealous of his wife's attention to their baby or teen-age son.

*Early fears of separation, loss and abandonment. Nancy Friday, in her recent book Jealousy (Perigord/William Morrow, $19.95), focuses in detail on such fears as deciding factors in adult jealousy. The maturation process of separation and individuation begins from 9 months of age to about 3, but as Friday writes, if the fear of separation isn't resolved "we may work on it the rest of our lives."

"When adult love is offered to the unseparated person," says Friday, "the response is regression, a rush back in time as if to find what we never received or never relinquished. It has all the components of life and death. So does our jealousy."

Friday goes on to support the theories of the late psychoanalyst Melanie Klein, who believed the basis for our adult envy lies with the young infant's rage over the power of the mother's breast. This rage is frightening throughout infancy and childhood: The child doesn't want to jeopardize the love and nurturance of the mother. But if the mother has been able to consistently show her child that he is special and is not being replaced, the normal destructive impulses are converted to a more secure and satisfied love, which is carried into a jealous-free adult life.

Expanding from this theory, Friday says that women feel more guilty over jealousy than men because when they feel enraged over the man's power to give or withhold love (as mother did) they break society's unwritten law that "women are not supposed to feel angry."

But Jerilyn Ross contends that "men don't feel the pain of jealousy any less than women -- they just express it differently."

"Men tend to get angry," says Ross, "while women feel guilty or depressed, asking, 'What is wrong with me that he went to another woman?' "

The contemporary jealousy scene is improving, according to Ross, because "more women are liberated and talking back, saying, 'It's not all right that you flirt with your secretary.' The double standard is no longer acceptable. Another change is that more and more husbands have to worry about their wives going off with another man, now that more women are in the workplace."

And a recent Psychology Today study on jealousy and envy of nearly 25,000 questionnaire respondents, typically in their early thirties, found few sex differences in how men and women experience jealousy. They did, however, find that in how we value and see ourselves, men "attach more importance to fame and wealth, while women were concerned with being well-liked and physically attractive."

The study also found that, at least among the magazine's readers, "men and women are equally likely to have affairs while in a committed relationship." And that "women are more likely to participate in jealous behavior, such as searching through a lover's belongings and extensively questioning a lover about past romances."

To Ruth, a 35-year-old divorce' whose marriage broke up over "the other woman," the whole issue of jealousy and mistrust has been "a long nightmare and a mystery."

Suspicious of her husband's bizarre behavior and long absences, Ruth resorted to opening his mail, although she says she hated herself for her driven mistrust. "When I found an earring stud in the car -- I don't have pierced ears -- and two airplane tickets, that did it for me.

"His affair came out in the open, we eventually divorced, but I was still obsessed with wanting to know everything about this woman, even though she moved away and he was dating other women.

"It's strange," says Ruth, "but I still can feel the rage of jealousy when the men I date bring up the subject of their ex-wives. Without even meeting these women, I'm jealous. I still have to work that one out."