Sources and licenses

Synopedia copies no commercial dictionary and no other thesaurus website. All its lists are built from the open sources below, downloaded from their origin, then sorted and grouped by meaning with rules measured on samples checked by hand.

Relations between words

• Wiktionary, the free dictionary (senses, definitions, examples, synonyms and antonyms by sense, usage and regional labels, translations), extracted by kaikki.org. License CC BY-SA 4.0.
• Open English WordNet 2025, derived from Princeton WordNet. License CC BY 4.0.
• Moby Thesaurus II by Grady Ward, public domain by grant of the author, and Roget’s Thesaurus of English Words and Phrases (1911), public domain, from Project Gutenberg. Used only together with other sources.
• Classic synonym dictionaries in the public domain in the United States, from Project Gutenberg: J. C. Fernald, English Synonyms and Antonyms (1914), Webster’s Revised Unabridged Dictionary (1913), S. Fallows (1898), R. Soule (1871), Putnam (1913).
• ConceptNet 5.7, used only together with other sources. License CC BY-SA 4.0.

Spellings, examples and word history

• VarCon (Kevin Atkinson, Benjamin Titze), American, British, Canadian and Australian spellings. Copyright notice: permission to use, copy, modify, distribute and sell this database is granted without fee, provided that the copyright notice appears in all copies.
• Tatoeba, example sentences written by its contributors. License CC BY 2.0 FR.
• Google Books Ngram (version 3, 2020), use of each word in printed books per decade. License CC BY 3.0.
• CMU Pronouncing Dictionary, number of syllables. BSD 2-clause license.

Frequencies and sorting

• wordfreq (Robyn Speer), how common each word is. Data under CC BY-SA 4.0.
• fastText word vectors (Common Crawl), to measure how close two words are and to draw the map of meanings. License CC BY-SA 3.0.

Usage notes

• The “Choose the right word” notes are short extracts from J. C. Fernald (1914) or from Webster (1913), both in the public domain, credited under each note.

Reuse

Definitions and relations from Wiktionary remain under the CC BY-SA 4.0 license; any reuse must credit Wiktionary and keep the same license. A mistake, a missing synonym? Write to us from the Contact page.