Amazon is the latest in a slew of tech companies acquiring AI startups, as the race to improve machine learning interaction heats up.

Earlier this week, the company partially acquired Angel.ai, which sells natural language processing technology, according to a TechCrunch report. Although Amazon didn't confirm the acquisition, it said that the startup's co-founder and CEO, Navid Hadzaad, had indeed joined the company.

The news comes just hours after Google announced that it had acquired API.ai, which helps developers build conversational interfaces and counts more than 20 million users. Terms of the deal were not disclosed. "API.ai offers one of the leading conversational user interface platforms and they'll help Google empower developers to continue building great natural language interfaces," said Scott Huffman, Google's VP of engineering, in a blog post on Monday.

It still remains unclear how Google plans to use API.ai, given that it already has tools for natural language understanding and speech recognition. On Wednesday, the company launched its latest mobile chat app, Allo, with the Google Assistant, with the connected "Google Home" expected to come later this year.

Also this week, Etsy announced that it had bought Blackbird Technologies, a startup that builds machine learning for advanced search. The idea, Etsy says, is to help users sift through the e-commerce giant's some 40 million listings, using features like predictive type-ahead, ranking, and spell check.

"Our team has already made substantial enhancements to the search and discovery process on Etsy, especially through features like Exploratory Search," said Chad Dickerson, Etsy's CEO, in a statement.