IPA: /ˈstiːpnəs/
KK: /ˈstipnəs/
The quality or condition of having a sharp incline or slope.
The steepness of the hill made it difficult to climb.
Steepness is formed from "steep" (from Old English *stæpe*, meaning high or abrupt) and the suffix "-ness" (meaning the state or quality of). The word "steepness" refers to the quality of being steep or having a high incline.
Think of the word 'steep' which describes something high or abrupt, and remember that 'steepness' refers to the quality of being steep.