IPA: /ˈkuːlnəs/
KK: /kulnəs/
The quality or state of being cool, which can mean either having a low temperature or being fashionable and impressive.
Her coolness in handling the situation impressed everyone around her.
Coolness → It is formed from "cool" (from Old English "col", meaning moderately cold) and "-ness" (a suffix meaning the state or quality of). The word "coolness" refers to the state of being cool or moderately cold.
Think of the word 'cool' which means moderately cold, and remember that 'coolness' describes the state of being cool.