Definition of -ous in English:

-ous

Pronunciation /əs/

suffix

  • 1(forming adjectives) characterized by; of the nature of.

    ‘dangerous’
    • ‘mountainous’
  • 2Chemistry
    (forming adjectives) denoting an element in a lower valence.

    Compare with -ic

    ‘ferrous’
    • ‘sulfurous’

Origin

From Anglo-Norman French, or Old French -eus, from Latin -osus.