Apple's iPad--still No. 1, but slipping.

Apple's iPad still reigns supreme among tablets, but its grip on the market is starting to loosen.

In the fourth quarter, Apple's tablet captured 75.3 percent of worldwide market share, easily besting Android-based devices' 21.6 percent share, according to market-research firm Strategy Analytics. However, those figures differ vastly from the third quarter when Apple had 95.5 percent share and Android had just 2.3 percent.

For 2010 overall, iPad's held 84.1 percent of the market, while Android devices accounted for 13.1 percent.

Despite the iPad's slip, Apple sold millions more in the fourth quarter compared with the third. Strategy Analytics reported that 7.3 million iPads shipped worldwide in the fourth quarter, up from the 4.2 million in the third quarter. All told, Apple shipped 14.8 million iPads last year, the firm said.

Just 100,000 Android units shipped during the third quarter of 2010. But in the fourth quarter, 2.1 million units hit store shelves. In total, about 2.3 million Android-based tablets shipped worldwide last year.

The vast majority of those Android units were likely Samsung's Galaxy Tab. Samsung announced in early December that it had shipped 1 million units worldwide since their release in November. A report from South Korea news agency Yonhap said Samsung shipped 2 million Galaxy Tab units last year altogether. However, the company would not confirm that figure when contacted by CNET last week.

Either way, 2011 is shaping up to be an even bigger year for the tablet market as a whole.

Market researcher IDC said earlier this month that it expects 44.6 million tablets to ship this year. IDC estimates that 17 million devices shipped in 2010.

At the Consumer Electronics Show earlier this month, a slew of companies, including Asus, LG, Motorola, and Acer, showed off their entries for the tablet market in 2011. And by year's end, the market is expected to be filled with devices to compete with Apple's tablet.

For its part, Apple is also expected to deliver a new entrant to the tablet arena with the iPad 2. So far, however, the company has been its typical, tight-lipped self on any details surrounding that potential device.