Datamuse
Datamuse operates a word-finding query engine and lexical search service for developers, educators, and creative-writing applications. The Datamuse API exposes a /words endpoint that finds words matching a rich combination of semantic, phonetic, orthographic, and vocabulary constraints (means-like, sounds-like, spelled-like, synonyms, antonyms, hypernyms, meronyms, triggers, rhymes, homophones, and more) plus a /sug autocomplete endpoint. Free for non-commercial use up to 100,000 requests per day with no API key required; commercial use, custom vocabularies, and higher rate limits are available via a paid commercial agreement. Datamuse also runs OneLook, OneLook Thesaurus, RhymeZone, Rimar.io, and CivicSearch — consumer-facing word search tools built on the same lexical infrastructure.
APIs
Datamuse API
The Datamuse REST API exposes two operations covering word-finding (/words) and autocomplete suggestions (/sug). The /words endpoint accepts a rich combination of constraint par...
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Datamuse API
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FinOps
Datamuse Finops
FINOPSFeatures
Reverse-dictionary semantic constraint finding words whose meaning matches an input string of any length.
Phonetic constraint returning words pronounced similarly to a given input using a text-to-phonemes algorithm.
Orthographic constraint with wildcard pattern matching (* for any chars, ? for a single char).
Twelve lexical relations including synonyms, antonyms, hypernyms, hyponyms, holonyms, meronyms, triggers, frequent followers/predecessors, rhymes, near-rhymes, homophones, and consonant matches.
Topics, left-context (lc), and right-context (rc) parameters skew results toward a document theme or surrounding words.
Optional metadata flags add definitions, parts of speech, syllable counts, pronunciations, and corpus frequency to each word.
Default Arpabet pronunciations or IPA via the ipa flag, drawing on the CMU Pronouncing Dictionary.
Default English (550k terms) and Spanish (500k terms) vocabularies; custom domain vocabularies available on request.
Intelligent prefix suggestions with spelling correction and semantic fallback when exact matches are unavailable.
Free non-commercial use up to 100,000 requests per day without an account or API token; HTTPS and HTTP both supported.
Prepends the result list with a record describing the query string, useful for one-shot word-metadata lookups.
Use Cases
Power flashcards, quizzes, and language-learning apps with synonyms, antonyms, and related-word lookups.
Drive rhyme finders, thesaurus add-ins, and reverse-dictionary lookups for poetry, songwriting, and copywriting.
Generate clues, fill patterns with sp wildcards, and validate word lists for crosswords, hangman, and word ladders.
Provide intelligent prefix suggestions with spelling correction in search bars and form fields.
Add definitions, syllable counts, and pronunciations to reading apps, ESL tools, and accessibility software.
Expand a user's search terms with semantically related words to improve recall in document or product search.
Look up word relations, frequencies, and pronunciations as features for downstream NLP pipelines.
Combine sounds-like, means-like, and spelled-like constraints to brainstorm brand, domain, or product names.
Integrations
Datamuse's flagship word search engine indexing 10M+ words across 1000+ dictionaries; built on the same backend.
Reverse-dictionary and thesaurus product available on web, as a Google Docs add-on, and as an iOS/Mac app.
Rhyming dictionary and writing tool partnered with Merriam-Webster, available on web and mobile.
Spanish-language rhyming dictionary and thesaurus powered by Datamuse's Spanish vocabulary.
Local government meeting search engine covering 700+ jurisdictions across the US and Canada.
Princeton lexical database supplying synonyms, antonyms, hypernyms, hyponyms, holonyms, and meronyms.
Source for Arpabet pronunciations and the basis for phonetic constraints (sl, rel_rhy, rel_hom, rel_cns).
Corpus underpinning frequency scores and the rel_jja, rel_jjb, rel_bga, rel_bgb statistical relations.
Source of definitions returned via the md=d metadata flag.
Corpus and embedding sources contributing to means-like and trigger relations.
Community plugin embedding Datamuse-powered thesaurus and reverse-dictionary directly into Obsidian.
Multiple community MCP servers (lacausecrypto/datamuse-mcp, pipeworx-io/mcp-datamuse, bhayanak/datamuse-mcp-server) expose the API to LLM agents.
Solutions
Up to 100,000 requests per day with no API key, no signup, suitable for prototypes, hobby projects, research, and non-commercial education.
Custom contract for production traffic in customer-facing applications, higher quotas, custom vocabularies, and SLA — pricing on request.
Domain-specific term lists (medical, legal, gaming, internal jargon) hosted on Datamuse infrastructure with all standard relations.