Political jokes have begun reappearing on television comedy shows after a 10-year absence. The word "strike" has reentered the vocabulary of factory workers, teachers and bank clerks. Prominent exiles are cautiously beginning to return home. College students have announced plans to reorganize their long-banned national union.

Signs of change, large and small, abound in Brazil these days. For the first time since seizing power in a coup here 14 years ago, the military rulers have given concrete indications of willingness to relinquish the "revolutionary acts" they have customarily used to silence, punish and suppress opposition.

President Ernesto Geisel took power in 1974 promising just such a liberalization as part of his program for a "slow and gradual" return to democracy. However, his rule has been marked by frequent reliance on arbitrary powers. It was not until this June that Giesel announced the first halting steps toward institutional reform.

Those reforms were passed into law by an eager and obedient congress late last week and are scheduled to take effect Jan. 1. Yet even as newspapers here publish a daily countdown to the D-day, Brazillians are already acting as if an era had ended and a freer and more open one had begun.

Reaction to the reforms, whose announcement was timed to have maximum impact on congressional elections scheduled for Nov. 15, has been close to euphoric in some quarters. The Journal do Brasil, probably the most influential newspaper here, greeted Geisel's June announcement with a headline that read: "The Dictatorship Is Over."

Particularly welcomed is the extinction of the hated Institutional Act No. 5, the key to the government's apparatus of repression over the last decade. It gives Brazilian presidents the right to close the National Congress, override the judiciary and the constitution, deprive elected officials of their mandates and suspend the political rights of any citizen.

Under the reform program approved Sept. 21, Geisel and his handpicked successor, Gen. Joao Baptista Figueiredo, will no longer be able to decree such sweeping punishments. Other provisions restore habeas corpus for prisoners accused of political crimes, revoke penalties against students engaging in political activity and pave the way for the formation of new political parties.

The elimination of the Institutional Act No. 5 and other symbols of military absokutism has had psychological effects that may well outweigh the content of the proposals themselves. With the rules of the political game now apparently changed, key players have begun probing to determine the new limits.

Almost inevitably, the Geisel reform package has generated demands for more liberalization. Church, judicial and opposition leaders, encouraged by the climate of more openness that the reform measures helped create, have complained that the government's program is a mere palliative that offers too little and comes too late.

The reforms were in fact, voted into law over the objections of the Brazilian Democratic Movement, the sole legal opposition party. Its leaders charged that the Geisel package's "safeguard" provision, allowing the declaration of a "state of emergency," leaves arbitrary powers still in the president's hands.

"Had this package been handed down in 1973, it would have been welcomed as a badly needed breath of fresh air," said an opposition party leader. "But the government is years behind the rest of the country, so we're stuck with reforms that are antiqued even before they go into effect."

"After 14 years in power, the military still has not learned that you can't make things change or not change just by putting an order on a piece of paper," said a prominent lawyer. "To gap between what they want to happen and what really is happening is going to continue to grow."

At the same time, though, Geisel and Figueiredo must contend with military hard-liners who feel that the reform package concedes too much. Such elements are said to feel that the new and more liberal climate will lead to social unrest-such as the wave of strikes that have hit Brazilian cities over the last four months.

With that thought in mind, one prominent commentator here has warned against the mood of hopeful optimism sweeping Brazil as the southern spring arrives by recalling what happened in Czechoslovakia 10 years ago. If the military under pressure from hard-liners, decides that things have gone too far, he argues, the "Brazilian spring" could very well have the unhappy endings as the famous "Prague spring."