IPA: /ˈkwaɪət.nəs/
KK: /ˈkwaɪətnəs/
The state of being calm and free from noise or disturbance.
The quietness of the library helped her concentrate on her studies.
Quietness → It is formed from "quiet" (from Latin "quietus", meaning at rest or calm) and "-ness" (meaning the state or quality of). The word "quietness" refers to the state of being quiet or calm.
Think of the state of being 'at rest' ('quietus') and how adding '-ness' indicates a quality. This helps you remember that 'quietness' means the quality of being quiet.