Open English Wordnet
Nouns
(n)asperity, grimness, hardship, rigor, rigour, severity, severeness, rigorousness, rigourousnesssomething hard to endure“the asperity of northern winters”
(n)severity, severeness, harshness, rigor, rigour, rigorousness, rigourousness, inclemency, hardness, stiffnessexcessive sternness“severity of character”, “the harshness of his punishment was inhuman”, “the rigors of boot camp”