In medicine, biological processes are split into two conventional parts, normal and pathological. Neither of them is a natural kind. Being Normal in medicine is not a statistical concept, but it is factitious and counterfactual as is a default concept it does not affirm anything positive, it excludes suffering and pain. One must distinguish Abnormal from Pathological and this chapter looks at the distinctions that split biological processes into two conventional parts, Normal and Pathological. Being abnormal is dimensional and admits of degrees, while being pathological is an al-or-nothing matter. Normal is factitious, so that being Normal is counterfactual much the same as frictionless planes in physics. Being Abnormal or Pathological is real and empirical: it covers diseases, incapacity, depression, and harmful, aversive, malfunctions, biological conditions directly affecting bodies or minds, which are the legitimate ports of access to medicine. Being pathological is logically prior to being normal, but being normal is clinically prior to abnormality. Medical language is at once descriptive and prescriptive.