Lingua Robot vs Merriam-Webster

Lingua Robot is a RapidAPI-hosted REST dictionary covering more than 800,000 English lexical entries — words, phrasal verbs, and multiword expressions — with definitions, pronunciations, and morpheme/lemma data returned as JSON, documented on a separate Apiary reference site rather than its own marketing homepage. A live unauthenticated request against its real RapidAPI proxy host returned a reflected `access-control-allow-origin` header plus `access-control-allow-credentials: true`, reconfirming CORS; its free Basic tier covers 2,500 requests/day (then $0.004 each), with paid Pro/Ultra/Mega plans ($10-$99/month) raising the daily ceiling.

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.