The spelling of the word "nigrities" may be challenging for some, but it follows the standard English pronunciation rules. The word is pronounced as /nɪˈɡrɪtiːz/ in IPA phonetic transcription, with the emphasis on the second syllable "GRIT." The word comes from the Latin word "nigritia," meaning "blackness," and refers to the condition of being dark or black. With some practice and familiarity with its origins, the spelling of "nigrities" can be easily mastered.
Black pigmentation.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.