Datamuse is a collection of free websites, mobile apps, and APIs designed to help people create and communicate more effectively.

OneLook is the Web's premier search engine for English words, indexing 10 million unique words and phrases in more than 1000 dictionaries and glossaries. More than a million unique users visit OneLook every month.

RhymeZone is the premier tool for creative writers of all kinds, combining the features of a rhyming dictionary and a thesaurus. It serves several million writers every month through the website and its iOS and Android mobile apps. Rimar.io is its new Spanish sibling.

OneLook Thesaurus, its Google Docs add-on, and Spruce are brainstorming tools that combine some of the features of these sites.

The Datamuse API is a lexical search service for developers. It's answering ... queries per second right now from hundreds of applications.