NEW YORK —The tech companies are at it again, trying to catch the blockbuster iPad in a race to win the tablet market.

Google on Friday began shipping its Nexus 7, which is smaller and less expensive than Apple’s iPad and is meant to compete with both that device and Amazon’s Kindle Fire.

This summer, Microsoft announced that it would create its own tablet, Surface.

And Amazon is working on a new version of the Kindle Fire, with a larger display, that could compete more directly with the iPad, according to a developer briefed on Amazon’s plans who did not want to be identified. Analysts also believe that Amazon is updating the Kindle Fire. Drew Herdner, an Amazon spokesman, declined to comment.

But Apple is hardly about to cede ground.

The company is developing a new tablet with a 7.85-inch screen that is likely to sell for significantly less than the latest $499 iPad, with its 9.7-inch display, according to several people with knowledge of the project who declined to be named. The product is expected to be announced this year.

Natalie Kerris, an Apple spokeswoman, declined to comment.

Apple’s plan for a tablet with a smaller screen is part of a textbook business strategy, to lure customers who want different sizes of tablets into the iPad product family, said analysts and technology industry executives.

The strategy would probably include devices with different prices and functions tailored to various uses, they said. The idea is to help Apple solidify its dominance in the tablet market even as the richest companies in the tech business are trying to figure out how to outflank Apple.

Leslie Grandy, a former ­Apple manager who is a consultant and an adviser to start-up companies, said a smaller iPad could be especially appealing to people who do not carry their iPads with them because they are too large and heavy. Although a 7-inch device is too big for pants pockets, Grandy said, it is a good size for women’s purses.

“I really do feel like this is the sweet spot for them,’’ Grandy said.

The most credible challenge to the iPad appears to be Google’s Nexus 7, an Android device that costs $199 and is of the company’s own design. With a 7-inch screen, the Nexus 7 has already won enthusiastic reviews for its software and battery life — and, of course, its size and price.

In addition to creating the Surface, which could go on sale as early as the fall, Microsoft has also agreed to invest up to $605 million in Barnes & Noble’s Nook business. The move helps bolster another Apple rival in the tablet market.