variant of -ous, added to stems of Latin origin, often with corresponding nouns ending in -ity: atrocious; hilarious.
Compare -eous.

Origin of -ious

Middle English ≪ Latin -iōsus (see -i-, -ose1) and Latin -ius (masculine singular adj. ending, as in varius)
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

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