IPA: /ˈluːkˌwɔːrmnəs/
KK: /luk'wɔrmnəs/
The quality of being only slightly warm, not hot or cold.
The soup was served with a noticeable lukewarmness that disappointed the guests.
Lukewarmness → It is formed from "lukewarm" (from Old English *hlēow-warm*, meaning moderately warm) and the suffix "-ness" (meaning the state or quality of). The word "lukewarmness" refers to the state of being moderately warm, neither hot nor cold.
Think of something that is 'moderately warm' — 'lukewarm' describes a temperature that is not too hot or too cold, and '-ness' indicates the quality of that temperature.