May 20, 1983

International One of the biggest protests in Warsaw since martial law was imposed 17 months ago occurred as about 20,000 Poles attended the funeral and marched for nearly two hours to the burial of a 19-year-old youth who died after being detained by the police. The signature of the outlawed union Solidarity was fastened to the front of the coffin. (Page A1, Columns 2-3.) Rifts among Western leaders may mark the economic summit conference in Williamsburg, Va., on May 28-30, Reagan Administration aides fear. They have sought to assure a harmonious meeting, but there are major differences between Washington and Europe, including France's charge that American budget deficits and high interest rates are damaging the world economy. (A1:4.)

The stock market registered a broad loss yesterday in less active trading as the Dow Jones industrial average fell 12.19 points, to 1,191.37. It was the first time the closely watched barometer has closed below the 1,200 level since April 25, when it closed at 1,187.21. William M. LeFevre, vice president of investment strategy at Purcell, Graham & Company, attributed the selloff to disappointment over the rate of increase in the gross national product in the first quarter and the day's sharp drop in bond prices. The Commerce Department reported early in the session that the gross national product rose at a seasonally adjusted annual rate of 2.5 percent in the first quarter, lower than expected.

The economy grew at a 2.5 percent annual rate, after adjustment for inflation, in the first quarter this year, slower than originally estimated, the Commerce Department reported today. The downward revision from an original estimate of 3.1 percent was a result of a sharper decline in inventories than had been assumed, however, and does not change the outlook for significantly stronger growth this quarter, economists said. Several measures of corporate profits released today left a mixed picture of business activity in the quarter. The Commerce Department's preferred measure, profits from current production, jumped 12.4 percent from last year's fourth quarter, after having slipped 1 percent in the fourth quarter. The better-known measure of after-tax profits declined 4.6 percent after falling 1.3 percent in the fourth quarter.

Time Inc. announced yesterday that it would spin off its large forest products business to concentrate on publishing and video operations. The forest products group accounted for $1.1 billion in revenues last year, or 32 percent of Time Inc.'s consolidated revenues of $3.6 billion. The group will now be incorporated as a separate company whose shareholders will be Time Inc. shareholders. Following the spinoff, Time Inc.'s principal lines of business will be the publishing of magazines and books, and video, which includes Home Box Office, the nation's largest cable service, with more than 12 million subscribers, and the American Television and Communications Corporation, the largest cable system.

The dance company of the innovative choreographer Twyla Tharp will make its only appearance in the New York area this season at 8:30 tonight in the C.W. Post Concert Theater in Greenvale, L.I. On the program are ''Sue's Leg,'' danced to the music of Fats Waller; ''The Fugue,'' which has no music (footsteps create polyphony); ''Short Stories II'' and ''Assorted Quartets.'' Tickets are $12.50 and $15. The campus is about an hour from Midtown Manhattan. Directions and reservations: (516) 922-0061. A MIME OF MASKS Daniel Stein, an American mime based in Paris, who has received impressive reviews, does not wear white-face. But in his latest work he does wear unusual masks, such as a door, a slide rule and, believe it or not, a 13-member chorus. The work, receiving its world premiere at the Dance Theater Workshop, 219 West 19th Street, tonight at 11, is called ''Inclined to Agree.'' It explores the nature of truth - symbolized by a curtain of plumb lines - and peoples' slanted points of view - manifest in tilted chairs and other objects. Mr. Stein says he's a ''concert move-ician,'' explaining that he ''plays'' movement, just as a musician plays music. Tickets: $6. Reservations recommended: 924-0077.