Are you a developer building a BOT application? Do you want dictionary data for learning and academic research purpose? Dictionary APIs have many use cases. There a many APIs that are free with a limited number of requests. Many of them allow unlimited access to their API in the paid version. These are the list of Dictionary APIs (freemium - Free + Paid) that you can use to build any tool or application.
Top Dictionary API
Oxford Dictionaries API. The Oxford Dictionaries API gives you access to our world-renowned dictionary data, including definitions, translations, synonyms, and audio pronunciations.
Merriam-Webster Dictionary API. A comprehensive resource of dictionary and thesaurus data powered by Merriam-Webster's trusted references. Affordable, comprehensive, and easy to use. Free for non-commercial use.
The Collins Dictionary API gives developers access to Collins’ flagship monolingual, bilingual, and learner’s dictionaries. It allows the integration of Collins’ definitions, translations, examples, phrases, audio pronunciations, etc.
WordsAPI. An API for the english language. Definitions, related words, rhymes, and more.
Wordnik for Developers. Wordnik provides information about millions of words through our developer-friendly RESTful API with a generous free tier.