IPA: //ˈbrɪsk.nəs//
KK: /brɪsknəs/
The quality of being quick, energetic, and lively.
The briskness of the morning air made the walk refreshing.
Briskness is formed from "brisk" (of uncertain origin, possibly from Middle Dutch "brisk", meaning lively or active) and the suffix "-ness" (meaning the state or quality of). The word "briskness" refers to the quality of being lively or energetic.
Think of the word 'brisk' which suggests liveliness or energy, and remember that 'briskness' means the state of being lively.