IPA: //ˈrɪɡərəsnəs//
KK: /ˈrɪɡərəsnəs/
The quality of being strict and demanding, often in terms of rules or standards.
The rigorousness of the training program ensured that all participants were well-prepared.
Rigorousness → It is formed from "rigor" (from Latin "rigor", meaning stiffness or severity) and the suffix "-ous" (meaning full of) combined with "-ness" (meaning the state of). The word "rigorousness" means the state of being full of severity or strictness.
Think of 'rigor' meaning strictness and 'full of' ('-ous') to remember that 'rigorousness' refers to the state of being very strict or severe.