If 2010 was supposed to be the Year of the Tablet, then 2011 might be known as the Year of the Tablet Wars. The fighting heated up April 15, when Apple filed a lawsuit against Samsung — one of its chip suppliers — alleging that the South Korean company’s Galaxy phones and tablets ripped off the look and feel of Apple’s iPhones and iPads. Then Samsung filed lawsuits against Apple in three countries this week, accusing the tablet pioneer of infringing Samsung’s patents for reducing power consumption and interruptions during data transmission.

The dueling lawsuits coincided with the arrival of new competitors in the lucrative tablet market: BlackBerry maker Research in Motion just released its Playbook tablet, and Taipei-based Acer started selling its Iconia Tab A500 tablet. In the next few months, Samsung is expected to release larger versions of the Galaxy.

The lawsuits and the stream of market entrants reflect the quickening shift to tablets, which some analysts project will overtake personal computers in usage. Even though Apple dominates the tablet market — it has sold nearly 20 million iPads since 2010 and occupies 90 percent of the market — rivals are not shrinking from the competition and the prospect of playing a long game of catch-up. Many analysts think Apple will own 50 percent of the tablet market into 2015.

“We wouldn’t try if we didn’t think we couldn’t compete,” said Nick DiCarlo, Samsung’s vice president of product planning and product marketing. “There’s a huge opportunity for innovation. There’s a lot of cool things to come.”

The mounting litigation over smartphones and tablets was inevitable, said Alan Fisch, a Washington lawyer representing Imperium (IP) Holdings, which is suing seven smartphone makers, including Apple, for allegedly infringing on patents related to image sensors.

“Intense patent fights generally result when paradigm-shifting technology comes to market,” Fisch said. “This was true for the airplane, television and disposable diapers. And it should be true for the next paradigm-shifting technology.”

In court papers, Apple claims that Samsung’s Galaxy devices are copycats that “slavishly” mimic the look of the iPhone and iPad, from the rounded corners to the touch-screen icons to the sleek boxes in which the devices are packaged. (The word “slavishly” appears three times in Apple’s lawsuit.)

In an earnings call with investors last week, Apple’s chief operating officer, Tim Cook, tried to be measured in his comments about Samsung, which supplies microchips for the iPhone and iPad. “I expect a strong relationship will continue,” he said. But he added that Apple “felt the mobile division of Samsung had crossed the line. . . . After trying for some time to work through the issue, we decided to rely on the courts.”

Apple declined to be interviewed about the lawsuits.

Kim Titus, a Samsung spokesman, said the company “rejects” Apple’s allegations but declined further comment. Samsung released short statements saying it wanted to protect its intellectual property.

Glynn Lunney, an intellectual property professor at Tulane University Law School, said Apple’s lawsuit against Samsung might really be aimed at Google, because its Android operating system powers the Galaxy and other competing mobile devices.

“Google may be the real target because they’re probably in the long run the real problem for Apple, not other tablet makers,” Lunney said. “But its lawsuit against Samsung certainly has a chance. My own sense is that consumers would not mistake a Samsung tablet thinking they were getting an Apple iPad. These are fairly expensive items. It’s not like you’re buying jars of pickles off the supermarket shelves.”

Even if Samsung never catches up to Apple, it still needs to compete against other Android tablets.

“Anytime you have a market with high transition costs — with a tendency to lock into one device because it’s hard to switch all your contacts into another device — people stick with what they have,” Lunney said. “The longer you can hold onto your lead time in the market, that can be a very durable market advantage not only for today but for some period of time.”