IPA: /ˈstrɛn.ju.əs.nəs/
KK: /ˈstrɛn.ju.əs.nəs/
The quality of being very active, energetic, or requiring a lot of effort.
The strenuousness of the hike left us all exhausted but satisfied.
Strenuousness is formed from "strenuous" (from Latin "strenuus", meaning active or vigorous) and the suffix "-ness" (meaning the state or quality of). The word describes the state of being vigorous or requiring great effort.
Think of being 'active' ('strenuus') and the '-ness' indicating a quality. This helps you remember that 'strenuousness' refers to the quality of being vigorous or requiring effort.