IPA: /ˈɑːrdʒuəsnəs/
KK: /ˈɑrdʒuəsnəs/
The quality or condition of being very difficult and requiring a lot of effort.
The arduousness of the hike made it challenging for many participants.
Arduousness → It is formed from "arduus" (from Latin, meaning steep or difficult) and the suffix "-ness" (meaning the state or quality of). The word "arduousness" refers to the quality of being difficult or requiring great effort.
Think of 'steep' or 'difficult' ('arduus') to remember that 'arduousness' means the quality of being hard to accomplish.