'Breathy" is a frequent description. "Willowy" says a former publishing colleague.

If the whispery tone, a hallmark of the Long Island upper crust into which she was born, surprises you, it's because unless you know her, or remember the televised White House tour she gave when she was the president's wife, you may never have heard it. If it's difficult to reconcile the instantly recognizable face of this commanding woman with the girlish voice, that's because she doesn't talk much for public consumption.

Jacqueline Bouvier Kennedy Onassis has not granted an interview in at least 25 years, as far as Nancy Tuckerman, her longtime press aide, can recall.

And the fact that Onassis turns 60 on Friday will be no occasion for changing her mind. There will be no leisurely stroll across the 400-plus acres of her Martha's Vineyard estate with Barbara Walters and television cameras in tow.

Instead she will probably celebrate with friends and family at her house on the Vineyard, where she takes up residence for the month of August.

Not that her reticence has ever stopped anyone from weighing in on her. From the young first lady to the stoic young widow to jet-set wife of Greek shipping magnate to book editor, she has delighted, moved, mystified, angered and always titillated the public. Her life has become iconographic of the jumble of late 20th-century America - enviable and tragic, lavish and sparse.

Her style has been emulated - the pillbox hats of the sedate Jackie Kennedy, those huge dark glasses of the stalked Jackie O - and her face may have been photographed more than any other woman's.

There have been scores of books on her - the latest a cornucopia of gossip and alleged detail that practically jumped off the presses onto the bestseller and countless magazine articles including a recent cover story in Life that boasts photographs taken from every year of the six decades of her life.

She's been the subject or inspiration of various television movies and films. Among the actresses who have taken a shot at portraying her or a Jackie-like figure are Blair Brown, Jaclyn Smith, and Jacqueline Bissett (who played opposite Anthony Quinn as an Onassis-type character in the critically scorned film, The Greek Tycoon).

"Celebrity" is too simple a term. Her status will always be more complex and more exalted by virtue of being a Kennedy and the woman who, when John F. Kennedy was murdered in November 1963, bore her grief as well as a nation's in a lonely, very public role, never faltering. No matter how many eccentric millionaires she dates or how extravagant she is rumored to be, or how much or little she works, the public will always forgive her. Or at least give her slack.

On the verge of her 60th birthday, she looks as fit as ever. She is also very wealthy - the result of a healthy inheritance from Aristotle Onassis and the best financial advice money and position can buy. Here, calculations are just speculative exercises, but her fortune has been thought to be upward of $200 million.

But - is she happy? After two seemingly difficult marriages to two famous men - Jack Kennedy and Ari Onassis - after being squired around town by the famous and the unctuous, she has been dating the same man, diamond merchant Maurice Tempelsman, for 10 years. He is short, portly, wealthy and a month younger than she is.

Tempelsman, a longtime Democratic supporter - he had met John and Jackie Kennedy in the '60s - last year contributed $85,000 to the Democratic party.

She is frequently told how well her children have turned out, and the troubled lives of some of their Kennedy cousins only makes Caroline and John look more remarkable by contrast. By all accounts, Onassis is a doting grandmother to Caroline's 13-month-old girl.

Depending on what you read, Onassis's relations with the rest of the Kennedy family wax and wane, but there remains a steady connection. She has eschewed many of the public events commemorating the anniversary of JFK's death; instead Onassis has been present at events like the announcement this past May of the new "Profiles in Courage" awards, which takes its title from the late president's book. And she attended the dedication of the John F. Kennedy Presidential Library in Boston in 1979. That day, President Jimmy Carter greeted Onassis - for the first time - with a big kiss from which she recoiled.

She makes a point of having Kennedy family members over to her Vineyard house for one big get-together each summer. "They've all got boats in the Cape, and they're sailing around and they all drop in on one another, and you never know who you'll see at one of those houses," says a family friend. She attends the younger Kennedys' weddings (like Maria Shriver's). When her children are in Washington, they usually drop by the Hill office of their uncle, Sen. Edward Kennedy, D-Mass.

No matter what else in her life may have changed in these last few years, her attitude toward publicity remains the same: She doesn't like it. It's not uncommon for Nancy Tuckerman to call people around the time of some Jackie-related event, like a book, and remind them not to talk.

Onassis is legendary for taking a dim view of those friends who do chat about her in the press.

Yet Jacqueline Onassis lives in the public light, often glows in it. Cameras often catch her beaming. (Consider her stunning unposed photo on the cover of Vanity Fair - albeit post-recent-facelift, according to the story inside the magazine.) At Caroline's wedding, didn't she know that leaning her head on Ted Kennedy's shoulder would make an exquisite photo op?

Far from reclusive or even shy, Onassis and Tempelsman attend large tony parties, like those that benefit a museum or foundation, dine in restaurants and go to theatrical openings. On the other hand, John and Caroline shun publicity, making few public appearances.

When Onassis showed up at the 1987 fall season opening of Martha Graham's dance company, eager photographers nearly trampled aging choreographer Agnes de Mille in an attempt to get a photo of Jackie. However, she's also been known to travel modestly, even on as pedestrian an airline as the now defunct People Express, trundling her own bags through the airport on a quiet Saturday evening.

Home - in New York - is a penthouse co-op on Fifth Avenue overlooking the Metropolitan Museum of Art. It is sumptuous - 12 rooms, estimates someone who's been there. "It's like you'd expect," says a visitor. "Out of Connoisseur magazine. Antiquey."