Synonyms API - Thesaurus

English thesaurus: synonyms, antonyms and related words for 147,000 words, ranked and grouped by meaning with part of speech and definitions. Handles inflected forms (running → run).

Authentication & base URL

Subscribe through one of our marketplace listings; your marketplace API key and base URL are shown there. All endpoints return JSON over HTTPS, served from a global edge network (typically 20–150 ms).

Endpoints

GET /v1/thesaurus/{word}

Synonyms and antonyms

Example

GET /v1/thesaurus/happy?limit=10

{
  "word": "happy",
  "found": true,
  "partsOfSpeech": [
    "adjective"
  ],
  "synonyms": [
    "felicitous",
    "blessed",
    "blissful",
    "bright",
    "golden",
    "laughing",
    "fortunate",
    "glad",
    "willing",
    "well-chosen"
  ],
  "antonyms": [
    "unhappy"
  ],
  "related": [],
  "senses": [
    {
      "partOfSpeech": "adjective",
      "definition": "enjoying or showing or marked by joy or pleasure",
      "synonyms": [
        "blessed",
        "blissful",
        "bright",
        "golden",
        "laughing"
      ],
      "antonyms": [
        "unhappy"
      ],
      "broaderTerms": [],
      "example": "a happy smile"
    },
    {
      "partOfSpeech": "adjective",
      "definition": "marked by good fortune",
      "synonyms": [
        "felicitous",
        "fortunate"
      ],
      "antonyms": [],
      "broaderTerms": [],
      "example": "a felicitous life"
    }
  ],
  "notice": "WordNet 3.0 Copyright 2006 by Princeton University (https://wordnet.princeton.edu/license-and-commercial-use). Pronunciations: CMU Pronouncing Dictionary."
}

English thesaurus: synonyms, antonyms and related words for 147,000 words, ranked and grouped by meaning with part of speech and definitions. Handles inflected forms (running → run).

Endpoint

• GET /v1/thesaurus/{word} — synonyms (ranked by how many meanings share them), antonyms, related (broader terms) and senses (each meaning with part of speech, definition, synonyms, antonyms and an example).

Why this API

• 147,000 words and phrases, synonyms grouped by meaning so you pick the right sense ("bright" as smart vs. as shiny).
• pos=verb gives only verb synonyms; inflected words resolve to their base form (running → run, cities → city).
• Fast, cached on a global edge network; simple JSON.

Use cases

Writing assistants and editors, word games, SEO and content rewriting, search query expansion, education and vocabulary apps.

Data: WordNet 3.0 (Copyright Princeton University, free for commercial use) and the CMU Pronouncing Dictionary.

Pricing

Free plan 500 requests/month, Pro 25,000 for $4.99, Ultra 150,000 for $14.99.

Pricing

Free plan with 500 calls per month, then Pro (25,000 calls for $4.99/month) and Ultra (150,000 calls for $14.99/month). See all plans.