variant of -ous, added to stems of Latin origin, often with corresponding nouns ending in -ity: atrocious; hilarious.
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British Dictionary definitions for -ious
suffix forming adjectives
characterized by or full ofambitious; religious; suspicious Compare -eous
Word Origin for -ious
from Latin -ius and -iōsus full of
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012