-ious

suff.

Having; having the qualities of; full of: bilious.

[Middle English, partly from Latin -ius and partly from Old French -ieus, -ieux (from Latin -iōsus).]

American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

-ious

suffix forming adjectives

characterized by or full of: ambitious; religious; suspicious. Compare -eous

[from Latin -ius and -iōsus full of]

Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

-ous

1. a suffix forming adjectives that have the general sense “possessing, full of” a given quality (covetous; glorious; nervous; wondrous); -ous and its variant -ious have often been used to Anglicize Latin adjectives with terminations that cannot be directly adapted into English (atrocious; contiguous; garrulous; obvious; stupendous). As an adjective-forming suffix of neutral value, it regularly Anglicizes Greek and Latin adjectives derived without suffix from nouns and verbs; many such formations are productive combining forms in English, sometimes with a corresponding nominal combining form that has no suffix; compare -fer, -ferous; -phore, -phorous.

2. a suffix forming adjectival correspondents to the names of chemical elements; specialized, in opposition to like adjectives ending in -ic, to mean the lower of two possible valences (stannous chloride, SnCl₂, and stannic chloride, SnCl₄).

[Middle English < Anglo-French, Old French < Latin -ōsus; a doublet of -ose¹]