Washington, a ceremonial city accustomed to taking in stride everything from the return of victorious armies to astronauts from outer space, welcomed home 52 Americans from the isolation of captivity in Iran yesterday with an unabashed, unashamed outpouring of emition. Their arrival touched off a display of feeling seldom equalled in the history of the nation's capital.

It was supposed to be a day of subdued greeting because of the suffering these Americans endured during their 14 1/2 months of imprisonment. Instead, it became a day of spontaneous national celebration unmatched in many years.

The formal part of the drama ended with the new president of the United States, Ronald Reagan, speaking exactly one week to the day after taking office, telling the returned Americans to "turn the page and look ahead," but also warning the world of lessons the nation draws from this episode.

"Let terrorists be aware that when the rules of international behavior are violated," Reagan said, "our policy will be one of swift and effective retribution. We hear it said that we live in an era of limits to power. Well, let it also be understood there are limits to our patience."

Responding to the president for the freed Americans, Bruce Laingen, the senior diplomat, referred to "the emotionally draining but beautiful experience that all of us have just had on the street of this magnificent city." They would all always have a "love affair" with the American people, he added.

That emotion was reciprocated. With cheers and songs, tears and fireworks, and everywhere a blizzard of flags waving along a processional route that began in the Maryland countryside and ended with the singing of "God Bless America" on the South Lawn of the White House, the people in the capital tried to tell their fellow Americans how they felt.

They lined the parkways, stood 20 deep along the traditional parade route of the presidents, and surged out into the streets behind the buses carrying the Americans on their way to the White House reception.

Police said some half a million people turned out, although those crowd counts always rank among the least accurate of the Washington sciences. But there was no mistaking the genuineness of their demonstrations of affection.

Their message was both simple and complex: that the ordeal of the people Americans had learned to call, simply, "the hostages" had become inseparable from that of the country they served; that their experience had unified the nation as no other event in decades; and that their liberation had ignited a surge of joyous national pride.

Behind all the emotions unleashed yesterday lay a story of unprecedented complexities and unlikely twists and turns. The homecoming ceremonies for these Americans brought to an end one of the most intensely frustrating periods of recent American life.

The seizing of the American at the U.S. Embassy in Tehran on Nov. 4, 1979, and their subsequent 444 days of imprisonment came to symbolize a decline of American power -- and a strong accompanying sense of American humiliation -- in a new age of international terrorism.

It became the dominant fact of the 1980 presidential election year, which ended, with fitting irony, one year to the day after the takeover, and culminated in melodramatic fashion on the nation's 49th Inauguration Day.

The bunting and flags from Reagan's inauguration were still largely in place at the Capitol, along Pennsylvania Avenue, and in front of the White House. Adding a different tone, and color, were strands of yellow ribbons everywhere.

In what seemed like the endless months of the hostage crisis, those ribbons had become the national symbol of remembrance for their captivity. Yesterday they decorated trees and marble columns, construction cranes and street lamps; and they were displayed, in countless ways, by tens of thousands of people.

The ceremonial tone for the day was supposed to have been low-key. Word had come from the White House earlier that some of the former hostages had developed severe psychological problems during their imprisonment. hBut nothing was going to keep those crowds from voicing their emotions.

The freed Americans landed at Andrews Air Force Base shortly before noon after a flight from near West Point, N.Y. and from the moment the first of three planes touched down the liberated Americans were bathed in a sea of sound.

Bands immediately struck up partiotic anthems -- God Bless America," "America the Beautiful," This is My Country" -- while the 52 people, some in civilian clothes, some in military uniforms, moved through a receiving line headed by Vice President Bush and Secretary of State Alexander M. Haig Jr. Then they boarded waiting buses for the procession into Washington.

Although the official welcoming ceremonies were held in Washington, this part of the hostage saga, like all those that preceded it, was participated in by the entire country. Americans awoke yesterday, as they have for so many months, to find their television screend dominated for one last time by the lives of the embassy personnel from Iran.

"Good morning, we continue to hear horror stories about the former hostages," was the way one network correspondent began his report from the scene at West Point, where the Americans had been in seclusion with their families since their arrival on U.S. soil Sunday afternoon. This was followed by more reports of beatings and other punishments inflicted on the Americans by their captors.

At 9 a.m. another in a series of live television productions permitted watching Americans to share more intimately in what had happened to their countrymen and women. An auditorium at West Point was turned into a huge setting for a live news conference with an army of reporters questioning 41 of the former hostages who sat behind microphones on long benches covered with blue cloth. It was the first time other Americans had an opportunity to see and hear from so many of the former captives.

The conference demonstrated that, reports of emotional problems to the contrary, most of these Americans appeared to have come through their experience relatively unscathed.

In their answers, they demonstrated good humor and good spirit. A Marine, John D. McKeel Jr., drew laughter when he said there was nothing wrong with them that getting back to chasing women wouldn't heal.

Another, John Earl Graves, public affairs officer of the embassy, offered what he knew would be intriguing ideas about the motivations of their captors. He had no doubt at all, he said, in reponse to a question, that the Iranians were indeed students, and that they used their demand for the return of the shah to Iran only as a pretext to take the Americans hostage.

But the general tone of the freed Americans was one of gratitude and humility. They did not consider themselves heroes, Bruce Laingen said. And at another point one of them, William J. Daugherty, remarked that, "The real heroes of this event have been the families."

It was Laingen, the principal spokesman for the group, who set the theme for them all, though, when he talked about the support of the American people as sustaining them throughout their months as hostages.

"Never has so small a group owed so much to so many," he said.

That kind of remark was heard often yesterday as the liberated Americans spoke of such things as "the celebration of love" they had experienced since their return and of their "undying respect "for the eight U.S. servicemen who lost their lives trying to rescue them last May after a mission that ended with charred American bodies and helicopters on the Iranian desert.

Reagan referred to that mission during his White House welcome yesterday afternoon.

"I'm sure you will want to know that with us here today are families of the eight heroic men who gave their lives in the attempt to effect your rescue," he said. Then, paraphrasing the Bible, he added, "Greater glory hath no man than that he lay down his life for another." The president told them that he had invited Col. Charles Beckwith and some of the men who survived that mission, along with the families of those who died, to the White House ceremonies.

"We ask God's special healing for those who suffered wounds and his comfort to those who lost loved ones," he said, just before closing. "To them, to you and to your families -- again -- welcome from all America, and thank you for making us proud to be Americans."

More than anything, else that note of pride was the unifying theme for this day of celebration that came so soon after the nation had finished the traditional rituals of renewal that accompany every presidential inauguration and shift of power.

Over the decades Washington has witntssed many memorable celebrations that have drawn the country, momentarily, into the capital. It has greeted kings and queens, princes and popes, returning warriors and assorted heroes, and it has seen processions of thousands of Americans demonstating for causes in which they believe, whether to end a war or renew a commitment to justice. What made yesterday's different was the nature of the celebration and the reaction of the people to the individual actors.

Yesterday the crowds were paying tribute to Americans who had not won wars, climbed previously unscaled mountains, flown the Atlantic alone or explored the distant heavens. They were saluting survivors, once faceless fellow citizens who suffered and endured. And they were saluting the successful end of an episode in which everyone, everywhere in the country had come to share.

You could see those elements anywhere you looked yesterday. When the buses lumbered by the crowds standing expectantly in front of the White House on a warm overcast January afternoon, the lines broke and people raced towards the vehicles. They shouted personal greetings, along with their cheers, to the freed Americans and their family members passing by them. They obviously felt they knew those people, and so did the entire country.

By their outpouring of spontaneous emotion they were signalling that they believed that something good could result from one of the most frustrating episodes of American history.

At the White House, during the official cermonies, Jack Cannon was describing the day as "one of the most moving experiences of my life." He's the State Department spokesman who has been handling news of the hostages since their return to freedom. Cannon then provided an impromptu summation for the day, and for that experience.

"It represents a national catharsis," he said. "I think the U.S. has been seeking out something like this for a very long time, and today they got it. It is almost ironic that out of a situation of abject failure comes finally something Americans can be really proud of."

With that assessment Washington the capital of controversy and disagreement, for once was in complete agreement.