A discontinuous variable is a term used in genetics and biology. It describes inherited individual characteristics, called phenotypes, which fall into unusual categories not measurable on a general spectrum. These characteristics include elements of bodily composition such as blood types, and behaviours such as the ability to roll one's tongue.
Variation in phenotypes has two categories: continuous and discontinuous. Continuous variables are measured on a scale of difference, like height, individuals varying from five feet to six feet tall, etc. Discontinuous variables are exclusionary. An example would be blood group; a person may be Type O or Type A, not both.