source

1 a point or place at which something is invented or provided <we were uncertain as to the source of the rumors> <a source of inspiration> Synonyms cradle, font, fountain, fountainhead, origin, root, seedbed, spring, well, wellspring Related Words beginning, commencement, dawn, day one, genesis, get-go (also git-go), inception, incipience, incipiency, kickoff, launch, morning, nascence, nascency, onset, outset, start, threshold; baseline, first base, ground zero, square one

2 the beginning part of a stream <19th-century explorers who sought the source of the Nile> Synonyms head, headstream, headwaterRelated Words fountain, fountainhead, geyser, headspring, hot spring, spring, wellspring; branch, feeder, tributary

3 something mentioned in a text as providing related and especially supporting information <the professor asked the students to have at least five different sources for their papers> Synonyms authority, referenceRelated Words citation, excerpt, extract, quotation; caption, cross-reference, footnote, note