LATIN DICTIONARYLexicon Latīnum
proper noun · masculinesecond declension

Sinnius

Sinnius m sg (genitive Sinniī or Sinnī)
Classical[ˈsɪn.ni.ʊs]Ecclesiastical[ˈsin.ni.us]

Meaning

  1. masculinesingulara Roman nomen gentile, gens or "family name" famously held by
  2. masculinesingularSinnius Capito, a Roman grammarian

Declension

declension
formsingularplural
nominativeSinnius—
genitiveSinniī
Sinnī		—
dativeSinniō—
accusativeSinnium—
ablativeSinniō—
vocativeSinnī—

Sinnĭus, ia,
I. the name of a Roman gens, e. g. Sinnius Capito, a Roman grammarian, Gell. 5, 21, 9.—Hence, Sinnĭānus, a, um, adj., of Sinnius: opinio, Gell. 5, 21, 14.

Quick answers

What does Sinnius mean in Latin?
Sinnius, a proper noun, means “a Roman nomen gentile, gens or "family name" famously held by”.
What is the genitive of Sinnius?
The genitive singular is Sinniī. Sinnius is masculine, second declension.
How do you pronounce Sinnius?
In classical Latin, [ˈsɪn.ni.ʊs]; in ecclesiastical (church) Latin, [ˈsin.ni.us].