(ˈ) ̷ ̷ at non- + noun
Usage: often attributive
1. : a substance that is not a protein — compare prosthetic
2. : any or the sum of all of the plant or animal nitrogenous constituents (as asparagine of plants or urea and uric acid of urine or various extractives of muscle) that are less complex in structure than proteins
nonprotein nitrogen