Merriam-Webster vs Words

Merriam-Webster's Dictionary API returns JSON definitions, pronunciations, and audio from the publisher's own Collegiate Dictionary and Thesaurus, plus specialized editions covering medical, learner's, Spanish-English, and grade-banded school dictionaries, each requiring a separate free API key. Keys are issued under a strict non-commercial license capped at 1,000 queries/day/key; using the service in a commercial product requires a separately negotiated agreement with Merriam-Webster.

WordsAPI is a RapidAPI-hosted REST dictionary/thesaurus returning JSON definitions, synonyms, antonyms, rhymes, pronunciations, and word-frequency data across more than 150,000 English words — its own docs still show code samples calling the deprecated `wordsapiv1.p.mashape.com` host with an `X-Mashape-Key` header, but that legacy domain now refuses every request and a current RapidAPI key against the live `.p.rapidapi.com` proxy is required instead. A live unauthenticated request against that real proxy host returned a reflected `access-control-allow-origin` header plus `access-control-allow-credentials: true`, confirming CORS; its free tier covers 2,500 requests/day before paid plans starting at $10/month raise the ceiling to 25,000+/day.