rigor

(noun) something hard to endure. Synonyms: asperity, grimness, hardship, rigour, severity, severeness, rigorousness, rigourousness. Example: "The asperity of northern winters."

(noun) the quality of being valid and rigorous. Synonyms: cogency, validity, rigour.

(noun) excessive sternness. Synonyms: severity, severeness, harshness, rigour, rigorousness, rigourousness, inclemency, hardness, stiffness. Examples: "Severity of character." "The harshness of his punishment was inhuman." "The rigors of boot camp."