It may be the very freedom to go all over the map that has made jazz dance the lingua franca of Broadway.

Think about the stellar Broadway jazz dancers and sooner or later you'll find yourself considering Gwen Verdon. Whether vamping an unwary young baseball player in "Whatever Lola Wants" in Damn Yankees or romping in a movie star's bedroom in Sweet Charity's "If My Friends Could See Me Now," Verdon epitomized the sassy, brassy dance style that has been the beating pulse of Broadway musicals front the 1930s to the present day.

But if you try to figure out what made her the great jazz dancer she was. things get a little tricky. Read her entry in The Oxford Dictionary of Dance: "She studied ballet with Ernest Belcher and Aida Broadbent and Spanish dance with Eduardo Cansino (Rita Hayworth's father); later studied ballet with Carmelite Maracci and East Indian dance with La Meri." Jazzdance? It doesn't show up until she joins the company of the seminal teacher-choreographer Jack Cole.

So let's take a look at his resume--surely there, before he worked Oil Kismet and A Funny Thing Happened on the Way to the Forum, is a clue to the genesis of jazz dance on Broadway. But no. In the 1930s, Jack Cole studied with legendary Ruth St. Denis and Ted Shawn, and performed with another pair of pioneering modernists, Doris Humphrey and Charles Weidman. And when he brought his own company--possibly with Verdon in the crew--to a ritzy Manhattan nightspot, the Latin Quarter, in 1947, he programmed an intense jitterbug number, a formal piece derived from East Indian dance, and a flamboyant Latin revel. The program seems to be all over the map--literally. And in a way, it may be the very freedom to go all over that has made jazz dance the lingua franca of Broadway: It's an idiom that works as well in Aida as it does in Hairspray or Bombay Dreams.

Those three shows don't appear initially to be speaking the same dance language at all. And at first glance, it seems easier to say what jazz dance isn't--it isn't ballet, it isn't modern, it isn't tap, it isn't ballroom, it isn't folk--than what it is. But the more you look at it, particularly on Broadway, you begin to see that, while jazz dance is distinct from ballet and modern and all the rest, it has borrowed from each of them. It may swing where ballet swoons, but where do those lifts and turns come from? It may smile where modern scowls, but what's with those muscle isolations and thrusting hips? Jazz dance does with movement what the great American theater composers--think Jerome Kern George Gershwin, Leonard Bernstein--did with notes: First they appropriated the characteristic sounds of spirituals, parlor ballads, and operetta songs and gave them the all-American meltingpot treatment; then they added a shiny coat of showbiz gloss. Jazz dance is an amalgam of American dance forms high and low--the barre and the bar, the waltz and the Watusi--adapted for maximum theatrical impact.

One has only to look at the style's greatest exponents from--Robert Alton, who was the outstanding early Broadway choreographer, to Luigi, who taught generations of Broadway dancers, to Jerome Robbins, whose West Side Story may be the finest example ever seen. They all came out of ballet. Alton, the choreographer of Anything Goes and Pal Joey for the stage and White Christmas and Daddy Long Legs for the movies, was a student of the Bolshoi dancer Mikhail Mordkin, who toured with Pavlova. Another of Pavlova's partners, the St. Petersburg-trained Adolph Bolm, taught Luigi--and so did Bronislava Nijinska and Eugene Loring. In fact, only a handful of Broadway choreographers--most importantly Gower Champion and Bob Fosse--were rooted entirely in show dancing. But if jazz dance began by borrowing from other forms, it has to be said that these days, it's hard to tell which way the influences flow. One of American Ballet Theatre's most successful new works in years is Within You Without You: A Tribute to George Harrison, and its most popular section is the one choreographed by Ann Retaking, an archetypal Fosse dancer. And pop music and jazz moves call be found in all manner of modern dance, from Garth Fagan to Mark Morris to Paul Taylor. Jazz dance may have come out of everywhere, but now it's in everything.

Sylviane Gold has written about theater for Newsday and The New York Times.