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; -pter, -pterous; -vore, -vorous.
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).
A Long List of Affixes: Suffixes, Prefixes, and Combining Forms
Suffixes -able, -ible, -ile: (form adjs) able to, fit to, worthy, capable; apt to; subject to being ~-ed -ac: one affect with -ac, -al, -ane, -ar, -ary, -ch, -ese, -ic, -ical, -id, -ile, -ine, -ish, -ory: like, of, pertaining to; characterized by -aceae: families of plants -aceous, -ous: resemblance to a substance; full of -acy, -age, -ance, -ancy, -asm, -dom, -ence, -ency, -hood, -ism, -ity, -ment, -mony, -ness, -ry, -ship, …
Origin of -ous
Middle English < Anglo-French, Old French < Latin -ōsus; a doublet of -ose1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
suffix forming adjectives
having, full of, or characterized bydangerous; spacious; languorous
(in chemistry) indicating that an element is chemically combined in the lower of two possible valency statesferrous; stannous Compare -ic (def. 2)
Word Origin for -ous
from Old French, from Latin -ōsus or -us, Greek -os, adj suffixes
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
word-forming element making adjectives from nouns, meaning "having, full of, having to do with, doing, inclined to," from Old French -ous, -eux, from Latin -osus (cf. -ose (1)). In chemistry, "having a lower valence than forms expressed in -ic."
Online Etymology Dictionary, © 2010 Douglas Harper
Possessing; full of; characterized by:filamentous.
Having a valence lower than that of a specified element in compounds or ions named with adjectives ending in -ic:ferrous.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.