The war to build the best tablet is shifting to software.

In the year-and-a-half since Apple Inc. (AAPL) released the market-leading iPad, other companies have tried to one-up the technology giant by going smaller, lighter and cheaper. Now, as the number of tablet entrants picks up, the competition is expanding to what the device can do and not just what it looks like.

On Monday, Amazon.com Inc. (AMZN) began shipping its new Kindle Fire, a $199 tablet packed with custom software that the Seattle company hopes will distinguish its device.

As their hardware starts to resemble each other's, software is the most defensible position tablet makers like Amazon have.

The same approach is being used by a variety of tablet makers trying to attack and expand the market beyond the iPad, which has unique software features tied to the device. The iPad currently commands a 70% share of the tablet market, according to Forrester Research and Piper Jaffray & Co. analysts, and has an ecosystem of some 140,000 apps for the iPad specifically.

Others are now racing to match the selection. Last week, Amazon issued two statements within two days about its software offerings, saying it secured 'several thousand' apps, including ones from online-video service Netflix Inc. (NFLX), game-maker Zynga Inc., and Walt Disney Co.'s (DIS) ESPN.

Tablet makers are still challenging each other on hardware too, though a more head-to-head battle likely won't come until next year. That's when Amazon will release another tabletcomputer with a touchscreen that is about 9.7 inches, according to a person familiar with the matter, instead of the 7-inch-size that began shipping this week. The iPad has a 9.7-inch screen.

The person familiar with the matter also said Amazon has five million Kindle Fire tablets on hand to sell during the holiday season.

It is unclear when the new 9.7-inch Amazon gadget would be sold. The Wall Street Journal earlier reported the company was working on another model it could release next year.

Apple, which makes the vast majority of its revenue from hardware, is also talking more about software these days.

In October, the company released iCloud, software for syncing content between Apple devices, its iMessage messaging service for tablets and some two hundred other software tweaks.

For its iPhone 4S that went on sale the same month, Apple didn't upgrade the hardware significantly and focused on the software, introducing new features like its Siri digital assistant.

Jessica E. Vascellaro / Stu Woo

• competition [,kɔmpi´tiʃən] n.比赛；竞争 (初中英语单词)
• device [di´vais] n.装置；器具；策略 (初中英语单词)
• shipping [´ʃipiŋ] n.船运业；船舶(总数) (初中英语单词)
• distinguish [di´stiŋgwiʃ] v.区分；识别；立功 (初中英语单词)
• resemble [ri´zembəl] vt.类似，象 (初中英语单词)
• variety [və´raiəti] n.变化；多样(性)；种类 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• release [ri´li:s] vt&n.释放；放松；赦免 (初中英语单词)
• computer [kəm´pju:tə] n.计算机；电子计算器 (初中英语单词)
• holiday [´hɔlidi] n.假日，假期，节日 (初中英语单词)
• journal [´dʒə:nəl] n.日记；日报；杂志 (初中英语单词)
• working [´wə:kiŋ] a.工人的；劳动的 (初中英语单词)
• tablet [´tæblit] n.碑；牌；匾额 (高中英语单词)
• kindle [´kindl] v.点燃；(使)激动 (高中英语单词)
• expand [ik´spænd] vt.张开；膨胀；扩大 (高中英语单词)
• unique [ju:´ni:k] a.唯一的 n.独一无二 (高中英语单词)
• selection [si´lekʃən] n.选择；选拔；精选物 (高中英语单词)
• saying [´seiŋ, ´sei-iŋ] n.言语；言论；格言 (高中英语单词)
• revenue [´revinju:] n.税收；收入 (高中英语单词)
• hardware [´hɑ:dweə] n.五金器皿 (英语四级单词)
• amazon [´æməzən] n.女战士 (英语四级单词)
• trying [´traiiŋ] a.难堪的；费劲的 (英语四级单词)