If you measure a theater season by the number, the range and -- dare I bring it up? -- the quality of the productions, cold analysis suggests this may have been Washington's best ever.

No season would be complete without its trifles and clinkers, of course. From 1980-81, "Tricks of the Trade," "A Partridge in a Pear Tree," "The Child," "Richard III," "Crossing Niagara and "Sarah in America" come readily to mind. But most of these efforts were, at least, wretched through and through. By contrast, there were mercifully few of those overblown pieces of mediocrity that we often confuse with great theater, while secretly questioning why we were bored stiff.

So much for the bad -- but, on the whole, forthrightly bad -- side of things. On to the good. I have been scrounging around in my attic of fond memories, and have emerged with a job-lot of mementoes -- enduring moments of total immersion in what was happening on Washington stages this season.

"Galileo" (Arena). I see the gluttonous astronomer, played by Robert Prosky, interrupting his labors to persuade a small boy that what looks like the sun crossing the sky is really the earth rotating on its axis. Galileo made this subverside point by picking up the boy's chair -- boy and all -- and telling him to watch a model of the sun while being rotated 360 degrees on his axis.

"Sweeny Todd" (Opera House). White-faced George Hearn, looking as if he had just returned from the grave (or perhaps a job in a flour mill), gave a magnificent performance as the Demon Barber of Fleet Street. I have warm memories of the reunion between Hearn and his barber's tools, which the loyal Mrs. Lovett had guarded over since the frame-up that sent him to Australia in chairs. "at last -- my arm is complete again?" Hearn proclaimed, fondling his razor and waving it high in the air. (It was his only show of affection for anything or anyone.)

As Mrs. Lovett, Angela Lansbury was no slouch either, Furiously hawking "The Worst Pies in London" and indignantly denying that she had ever put cat meat into a pie. "Just the thought of it's enough to make you sick," she sang, "and I'm telling you them pussycats is quick."

"Children of a Lesser God" (National). This was another touring production that imrpoved on the Broadway original. Linda Bove and Peter Evans had more chemistry than Phyllis French and John Rubinstein, good as they were. Evans had to act and interpret for the deaf characters simultaneously, and managed to do so without making us overly conscious of it. Bove brought out the flirtatiousness and physically of the heroine, who refused to learn to talk because "I don't do things I don't do well."

"Romeo and Juliet" (Folger). The Folger Theatre's current production, directed by Michael Tolaydo, strips "Romeo and Juliet" down to its essentials -- two impetuous lovers, their feuding kin, and the events of a few days in Shakespearean Verona. Too often, the play has been pumped up into something grandiose, and the characters have seemed to be fighting or loving for eternity's sake rather than their own. Here, when the Capulets confront their daughter about the company she has been keeping, we see a pair of agitated parents and a child taking her first rebellious steps in life. They sit on her bed and comfort and cajole and berate her, and suddenly (as acted by Earle Edgarton and Marion Lines) they are real people, not mere devils ex machina.

And Margaret Whitton (about to leave for a role in New York) makes a wonderfully flightly and playful Juliet. No, she doesn't look 14, but her approach to life and love is a 14-year-old's.

"The Man Who Came to Dinner" (Arena). This free-form, farce-minded production stretched the limits of both the play and the Arena copany -- and both showed admirable elasticity. There were many jolly moments, but one that sticks in my mind, for no very good reason, involves Terrence Currier as the much-abused physician charged with treating Sheridan Whiteside's injuries. Kaufman and Hart gave the character many humiliations to endure. The Arena production gave him a new one -- being enlisted as piano accompanist when it came time for Richard Bauer (as the Noel Coward-like "Beverly Carlton") to sing. Carlton should have played his own piano, of course, but if the actor doesn't know how, what are you going to do? Instead of being embarrassed by the poly, director Douglas Wager made a joke of it. He made it just another of the diversions that kept sidetracking the doctor's efforts to get Whiteside's help on a memoir of "40 years as an Ohio general practitioner."

"A Raisin in the Sun" (studio). This was an uneven production, but mighty effective in the clutch, and Alfie Brown -- with a voice like a pipe organ and dimensions to match -- made the character of Lena Younger a memorable vision of old-fashioned, unpermissive Christian motherhood. When she gave her son what-for, the whole audience felt the reprimand in its bones.

"Disability" (Kreeger). Arena's spring "Carousel of New Plays" never really got spinning, but this, for me, was the standout of the group -- an angry, not always coherent, murderously funny portrait of a quadriplegic's imprisoned existence under the custody of possessive, marshmallowish parents. Through a classified ad ("Sexy, paralyzed young man, age 27, who wishes to meed sexy rich girl, 21 to 25"), the hero arranged a blind date. But her arrival in an electric wheelchair (just like his own) was a shock -- he had expected her to be normal. Charles Janasz and Christina Moore made the meeting and maneuvers of these two a suspenseful battle of wits on wheels.

"Amadeus" (National). This was, I persist in believing, a shallow play, betrayed by drab language and a misty-headed view of the nature of genius. But whatever you think of "Amadeus'" substance, it had sensationally theatrical scences, especially in the first act. There was the hack composer Salieri's first encounter with Mozart, making him suffer through a piddling little march written in his honor. As Tim Curry played Mozart, his impatience went to his feet -- and when he sat down at the harpisichord and improvised a few variations that improved the piece and about 800 percent, we could see, in Ian McKellen's quiet facial contortions, the birth of a first-class hatred.

"The King and I" (Warner). Those of us who have never been to Thailand may wonder if a Siamese king ever lived, or could have lived, who was anything like Yul Brynner. But if not, I ask you: Is Siam better off for it?

"The Little Foxes" (Eisenhower). Elizabeth Taylor's presence, voice, timing and eager participation in the Hubbard family's scraps and inspired people with low expectations of her stage skills to think again. There were irregular notes in the performance -- she wasn't nearly malevolent enough in the third-act battle with her husband -- but she made a strong impression. And although Regina Hubbard Giddens had never seemed so vain or gushy before, isn't an actress entitled to a new interpretation? minute examination. But the mood it aimed for was struck perfectly by Anthony Zerbe as brother Ben (with his unforgettable pronunciation of the word "aristrocrat" -- "aaahhrristocrat," accent on the first syllable). "The Little Foxes" was best appreciated as a lusty, vivid, vigorous piece of ensemble acting. Even with six and seven actors on stage at once, we knew what each character was thinking and feeling about each of the others -- a credit to the author as well as the cast.

"The Flying Karamazov Brothers" (Arena -- Old Vat Room). The performance was billed as "Juggling and Cheap Theatrics," and is stands in an undefinable corner of the 1980-81 season all by itself. Who can forget the gypsyish figure on one "Paolo Barechesto," "animal to friends," about the juggle two live cats and a stuffed rabit? "But please, ladies and gentlemen, don't worry," he said as he plucked the sorry beasts from their box. "There is no danger to myself."

There was more to the season. Arena Stage celebrated its 30th anniversary with furious activity and typical unpredictability. The choice pickings included a poignantly comic "American Buffalo" with Stanley Anderson and Kevin Donovan as Chicago low-life; Anderson's virtuoso performance in "Kean"; Richard Bauer's triumph in "The Suicide"; and an ingeniuously staged, extremely likable "God Bless You, Mr. Rosewater."

The Kennedy Center offered, along with some of its weakest selections ever, the idiotic but diverting kitsch of "42nd Street" and the class and craft of Gregory Hines and Co. in "Sophisticated Ladies," both at the Opera House; plus, at the Eisenhower, Gilda Radner's hyper-kinetic debut in Jean Kerr's "Lunch Hour"; Geraldine Page, Julie Harris and Rip Torn doing their best to make "Mixed Couples" add up to something; the old-fashioned, heart-tugging, stiff-upper-lip drama of "The Winslow Boy;" and, just-departed, the artful brilliance of Ralph Richardson in "Early Days."

The National Theatre, newly connected to the Shubert Organization, was well-populated with shows and audiences -- surely one of the best developers of the 1980-81 season.Besides "Amadeus" and "Children of a Lesser God," the National sponsored two Neil Simmon pieces ("They're Playing Our Song" and "I Ought to Be in Pictures") and a very acceptable resuscitation of "Brigadoon."

The Folger Theatre Group put together a solid season, including an admirable "Measure for Measure" and, on the new-play front, "How I got That Story," a surrealistic Vietnam comedy. Elsewhere, there was Jim Leonard's "The Diviners," an unusually solid play and production at the New Playwrights' Theatre; the terrific ensemble work of the Source Theatre's "for colored girls . . ."; and a further general proliferation of small theaters and nomadic theater companies.

Unfortunately, two trends threatened to mark this season as an aberration rather than a launching pad for bigger things to come. One is an apparent thinning out of audience support for the nonprofit institutions that make theater tick in Washington. Ralph Richardson played to houses that were half and two-thirds empty -- the low point of a consistently disappointing season at the Kennedy Center. "How I Got That Story" also failed to draw the audience it deserved. Some of Arena's most enterprising productions faced an uncommon number of empty seats.

And all this happened just when federal support for the arts faced the threat of a 50-percent cut. However you view it, it is going to be hard for Washington's theaters to sustain, no less expand on, their current accomplishments.

When unusual numbers of tickets go unsold, many explanations are offered. Perhaps the theater boom has moved too fast here -- or faster, at any rate, than the audience boom. Perhaps our producers have chosen poorly, particularly where new plays are concerned. The Kennedy Center certainly has -- and in addition to forfeiting audience confidence in its institutional judgment, it has done little to establish an identity that might transcend the ups and downs of individual productions, or to make theatergoers view the Center as an exciting place to be.

A good omen is the prospect of a centralized discount-ticket booth downtown. New York, with its two ticket booths and other marketing innovations, has created a whole subclass of younger, less well-heeled theatergoers willing to suffer long lines and other indignities in order to buy cut-rate tickets (tickets which probably wouldn't sell at the full rate). If theater in Washington is to continue growing and diversifying, it follows that the audience has to do the same.

The woes are easy to exaggerate. There was more theater here this season than ever and, if you're a chauvinist about these things, much more than in most American cities of comparable size. But the time to worry about falling behind is, needless to say, when you're ahead.