the word 's' in this words 'diabetes' does not mean the form of plural. 'diabetes' by itself means diabetes. :diabetes. https://ejje.weblio.jp/content/diabetes :diabete. https://ejje.weblio.jp/content/diabete
:Why "chalk" doesn't use plural in the sentence"Does he eat chalk". https://hinative.com/questions/14629840 :Associations to the word «Chalk. https://wordassociations.net/en/words-associated-with/Chalk