More e-commerce sites are using the made-up marketing term of Cyber Monday as a promotional event this year.

Monday is officially Cyber Monday, according to Shop.org, an industry trade group offshoot of the National Retail Federation, which represents brick-and-mortar retailers.

Shop.org devised the term in 2005 on the assumption that office workers back in their cubicles on the Monday after Thanksgiving took long breaks from their paid duties to shop online.

According to a Shop.org survey released Sunday, about 84 percent of retailers will have a special promotion for Cyber Monday, up from 72 percent last year.

Gap.com, for example is offering a 15 percent discount and free shipping on any purchase, Harry & David is offering 20 percent off of any purchase of $100 or more, and Bath & Body Works is offering a 25 percent discount on online orders.

Many e-commerce sites including Amazon.com offered promotions on Thanksgiving and the Friday after.

Unlike the brick-and-mortar world’s annual spike in sales on Black Friday, Cyber Monday isn’t the busiest shopping day of the year for Web retailers, said Craig Berman, spokesman for Amazon.com. The concept is shunned by many as yet another ploy designed to generate more hype around the season.

“We look at the holiday season as a whole rather than zeroing in on one day,” said Mr. Berman. “We may be using the term Cyber Monday on our Web site, but I don’t think so. We have daily deals, not just on one day. That’s served us well with our customers.”

Amazon.com, the Web’s largest e-tailer, said its busiest day last year was Dec. 10. In fact, every year, its sales volumes swell in the second week of December. This year the company’s biggest day is again expected to be sometime between Dec. 8 and Dec. 12, he said. That’s when shoppers are motivated to catch free shipping deadlines before they expire.

Web traffic from home and work increased 10 percent on Black Friday, growing from 28.8 million unique visitors in 2007 to 31.7 million unique visitors in 2008, according to preliminary results from Nielsen’s Online Holiday Shopping Index.

Online spending was up only 1 percent on Black Friday to $534 million, according to comScore Inc.

Through Nov. 28, $10.41 billion has been spent online, marking a 4-percent decline vs. the corresponding days last year, comScore said Sunday. But Thanksgiving Day and Friday online sales together were up 2 percent compared to last year.

“Last year and this year, we’ve seen more and more people shop online on Thanksgiving Day,” Mr. Berman said.

According to a Shop.org survey, conducted over the weekend by BIGresearch, 84.6 million consumers plan to shop online from home or at work Monday, up from 72 million in 2007 and 60.7 million in 2006. The survey found that 37.2 percent of adults will shop on Cyber Monday, up 16.6 percent over last year (31.9 percent).

E-commerce sales have been slowing this year. The U.S. Census Bureau said earlier this month that e-commerce sales increased 5.7 percent in the third quarter - only the second time the quarterly increase wasn’t in double digits since the measurement started in 1999.

Online sales increased 0.3 percent from the second quarter of 2008, which also had less growth than other quarters.

Still e-commerce sales are doing better than total retail sales, which declined 1.4 percent from the second quarter and increased a modest 0.3 percent from a year ago.

Growth in online sales is expected to beat brick-and-mortar results in November and December too.