/suy"teuh seen', -zeen', -sin/ , n. Biochem.
a pyrimidine base, C 4 H 5 N 3 O, that is one of the fundamental components of DNA and RNA, in which it forms a base pair with guanine. Symbol: C Cf. cytidine, cytidine monophosphate .
[ Cytosin (1894); see CYTO-, -OSE 2 , -INE 2 ]