Meaning of -ITIOUS in English

-ITIOUS

1.

suffix forming adjectives corresponding to nouns in -ition (ambitious; suppositious).

Etymology: L -itio etc. + -OUS 2.

suffix forming adjectives meaning 'related to, having the nature of' (adventitious; supposititious).

Etymology: L -icius + -OUS, commonly written with t in med.L manuscripts

Oxford English vocab.      Оксфордский английский словарь.