IPA: /ʌnˈkaɪndnəs/
KK: /ʌnˈkaɪndnəs/
The state or quality of being not nice or friendly to others.
Her unkindness towards her classmates made her very unpopular.
Unkindness → It is formed from "un-" (meaning not) and "kind" (from Old English "cynd", meaning nature or character) and "-ness" (meaning the state of being). The word "unkindness" refers to the state of not being kind or lacking kindness.
Think of 'not' ('un-') being added to 'kind' — this helps you remember that 'unkindness' means the state of lacking kindness.