"Chemistry" is the most popular word used by National Basketball Association general managers and coaches when talking about why some talented teams are successful and others are not.

The success of any sports franchise depends on solid financial foundation, strong, consistent leadership and excellent appraisal of talent. There are teams, however, that seem to have all these ingredients, that seem to have enough talented players, and still don't win consistently.

Once management assembles the best players possible, chemistry often makes the difference between winning and losing.

"It's hard to describe, but once you have it, you know it," said Don Nelson, head coach and director of player personnel at Milwaukee. "We had it when I played with the Celtics and I think we've got it in Milwaukee. It's a certain feeling that everything fits, nothing is lacking."

Basketball, perhaps more than any other sport, relies on teamwork, on players blending together, on compatible personalities, for success.

In baseball, the third baseman and right fielder could go an entire season without speaking and it wouldn't affect the team's performance. In football, the offensive players have very little in common with the defensive unit. In hockey, passes are made largely by instinct, goals on reaction and individual statistics and egos are not as important as in basketball, where a player can more readily alter another's performance by ignoring an open man or not helping defensively.

Off-the-court relationships are more important in basketball than in most other sports because of the small rosters. There is an intimacy that doesn't exist on larger squads or teams that don't travel almost daily. In other sports, there are enough players to conceal personality conflicts. On an NBA team, with only 12 players traveling together, it is difficult to avoid daily confrontations of antagonists.

Bullets General Manager Bob Ferry says that personality conflicts are not a problem as long as they don't carry over into the games. For example, Wes Unseld and Elvin Hayes had diametrically opposite personalities, very little in common and probably didn't eat three meals together during the nine years they traveled with the Bullets. Yet on the court they consistently helped each other.

"Getting along with each other doesn't have anything to do with team chemistry," Ferry said. "It's a dependency, knowing that you need each other, that you need the coach. That's what it's all about. It's like a marriage. What really binds a good marriage is knowing that you need each other. If for some reason you lose that need, a lot of times the marriage crumbles."

One team that was put together quickly and crumbled almost as fast was the 1976-77 Portland Trail Blazers. They combined the passing of Bill Walton, the powerful rebounding of Maurice Lucas, and the relentless running of Bobby Gross on a front line that contained all the ideal ingredients. The back court consisted of rookie Johnny Davis and Lionel Hollins, in his second season.

The Trail Blazers won 50 of their first 62 games the season after they won the title. Then Walton got hurt. Without the center's clever passing, Gross was just an ordinary forward and the guards became so ineffective that Coach Jack Ramsay let them go within three years. Once the team started to dissolve, Lucas became disenchanted and demanded to be traded. The Trail Blazers have had little success since.

An excellent example of a team's chemistry crumbling this past season is the New York Knicks. The previous year they won 50 games, but a good young guard (Ray Williams) was let go and two former stars (Randy Smith and Mike Newlin) were brought in to replace him. The Knicks wound up with five former all-stars with huge salaries and nobody felt dependent on anyone.

In contrast, the young Bullets knew they needed Coach Gene Shue's experience and guidance, particularly on defense. None of the players were established stars, so they felt they needed help from their teammates to be successful. They won 10 more games than the more talented Knicks.

"The single most important ingredient in gaining the right chemistry is hiring the right coach for the right situation," Ferry said. "We hired Gene because we knew the team had to be rebuilt. He had rebuilt teams before, he knew the personnel around the league and the players had to respect him.

"A coach can instill a dependency in the players by setting up a defense that is based on helping out and an offense that requires several passes and good picks to get an open shot," Ferry said. "Every player then realizes that he needs the help of his teammates to make a play work."

A key to winning in the NBA is to obtain the type of players who can blend together and do all the things necessary in order to be consistently successful. Five all-stars, five great shooters, five tenacious defenders won't do it.

"You need all kinds of players to win in this league," Philadelphia Coach Billy Cunningham said. "That's why Caldwell Jones is so important to us. Caldwell doesn't have to shoot to be happy. He's willing to let the others score and do all the dirty work. Those kind of guys are hard to find."

Boston and Philadelphia, finalists again in the Eastern Conference playoffs, went through the season with back courts made up of a small, quick penetrating playmaker and a larger, defense-conscious running mate (Tiny Archibald and Chris Ford or M.L. Carr for the Celtics, Maurice Cheeks and Lionel Hollins for the 76ers).

When asked why Chicago--another major disappointment--tumbled from 45 victories to 34 this season, several general managers cited the loss of Bobby Wilkerson.

Wilkerson averaged only 10 points a game for the Bulls, but when he signed with Cleveland as a free agent, Chicago was without a defensive guard who could rebound and get the ball inside to Artis Gilmore.

"Wilkerson may not fit in that well at Cleveland, but he was very important to Chicago," said K.C. Jones, an assistant coach at Boston who realizes the value of defensive guards. "He's one of those guys who isn't appreciated until he leaves."

Fitting the pieces together is the never-ending challenge of general managers and coaches. Robert Parish never was selected to the all-star game while at Golden State; now he's rated one of the league's most valuable players. He fit in at Boston.

Freeman Williams led San Diego in scoring last season with a 19.3 average. This year he was traded to Atlanta and rarely got off the bench. He didn't fit in.

"Everybody is always looking to improve, there's only one champion," said Ferry. "But getting more productive players doesn't always mean you're improving your team."

In this era of free agency, teams like Kansas City, Indiana and Cleveland are having difficulty competing with more affluent rivals because of their limited resources, location and losing traditions.

Kansas City lost its two top scorers last summer when it couldn't match Cleveland's offers for free agents Scott Wedman and Otis Birdsong. The Kings finally worked a deal, trading Birdsong to New Jersey for Cliff Robinson. Then they had to let that promising young forward go to the Cavaliers in February because he was on the last year of his contract and they wouldn't have been able to keep him, either.

Indiana lost its 7-foot center, James Edwards, as a free agent. The Pacers were so hard-pressed for cash during the season that they had to sell one of their most dependable rebounders, Mike Bantom, to Philadelphia for a mere $100,000.

Cleveland signed several free agents last summer, including Wedman and Edwards from Indiana, but not its top choices. At the head of the Cavaliers' most wanted list were Parish and Ray Williams, but no amount of money could make those two spend their winters in Richfield.

Cavaliers owner Ted Stepien grew up in Pittsburgh and has lived in Cleveland since 1937, but he realizes that Richfield, Ohio, is not the garden spot of the NBA. He knows many players will work for less money elsewhere, particularly if there's a chance to win a championship.

It's easier, of course, for Los Angeles to sign Bob McAdoo than New Jersey, just as it was easier for Boston to retain Parish. As long as the players have freedom of movement, the rich will get richer and for the rest it will be increasing difficult to acquire the proper chemistry.