Definition from Wiktionary, the free dictionary
Alternative forms 
- Used to form adjectives from nouns.
- (chemistry) Used in chemical nomenclature to name chemical compounds in which a specified chemical element has a lower oxidation number than in the equivalent compound whose name ends in the suffix -ic. For example sulphuric acid (H2SO4) has more oxygen atoms per molecule than sulphurous acid (H2SO3). See Inorganic nomenclature.
Derived terms 
Note - translations of English words ending in -ous do not necessarily end in the suffixes listed below.
suffix to form adjectives
chemical compounds in which a specified chemical element has a lower oxidation number
See also 
Old French 
- Alternative form of -us.