The stock market came off a week of record-breaking trading volume by easing today, with the Dow Jones Industrial Average declining almost nine points.

Profit-taking helped pull the Dow average down to 883.47, with 75 million shares traded on the New York Stock Exchange. Another negative factor was the Federal Reserve Board's decision Thursday to drop the discount rate, a key interest rate, by just a half point, said some analysts, who had been hoping for a deeper reduction.

Nationwide turnover in NYSE-listed issues, including trades in those stocks on regional exchanges and in the over-the-counter market, totaled 87.47 million shares.

Volume for the week on the New York exchange was nearly 550 million shares, after yesterday's one-session record of 137.3 million shares.

Several market forecasters predicted today that the drop-off would continue, with the market sliding back 50 points or so during the coming couple weeks of trading before resuming its dramatic recent surge. The Dow industrial average, the most closely watched market barometer, has risen by more than 107 points in the past two weeks.

American Express Co. today replaced Manville Corp. as one of the 30 securities which make up the Dow industrials. Manville filed for reorganization under bankruptcy laws Thursday, and the New York exchange said the stock would be suspended Sept. 10.

Meanwhile, on the New York exchange, just over 1,000 stocks declined, while 536 advanced in price. The average price per share fell by 32 cents. Bond prices fell by a point to a point and a half in light volume despite the announcement that the money supply rose for the week by $1.4 billion.

The NYSE's composite index slipped 0.78 point to 67.23, Standard & Poor's index of 400 industrials fell 1.57 points to 130.75, and S&P's 500-stock composite index was off 1.44 points to 117.11.

Cities Service led trading on the Big Board and was up 3/4. Otherwise, the most active stocks were off today, with Manville down 2 3/4, Martin Marietta, the target of a Bendix Corp. takeover bid, down 1 1/4, and American Telephone & Telegraph also down 1 1/4.

On the American Stock Exchange, volume also dropped sharply from 10.45 million shares yesterday to 5.5 million today. The Amex index fell by just 0.96 point, closing at 275.41, as 320 stocks declined, 246 rose and another 232 issues remained unchanged.

The over-the-counter market was off slightly, too, with the NASDAQ composite index off 0.57 point to 177.60.