Definition of -ness in US English:

-ness

suffix

  • 1(forming nouns chiefly from adjectives) denoting a state or condition.

    ‘liveliness’
    ‘sadness’
    1. 1.1 (forming nouns chiefly from adjectives) an instance of a state or condition.
      ‘a kindness’
  • 2(forming nouns chiefly from adjectives) something in a certain state.

    ‘wilderness’

Origin

Old English -nes, -ness, of Germanic origin.

Pronunciation

-ness

/nis/