TypeA

Type A is a term used as a label in multiple classification systems across fields such as medicine, psychology, technology, and biology. It is not a single concept but a shorthand for a category that is contrasted with other types (such as Type B).

In the ABO blood group system, Type A refers to red blood cells that carry the A antigen on their surface. People with type A blood typically have type A or O blood as possible donors and can receive from type A or O donors, depending on additional antigens and the Rh factor. Subtypes such as A1 and A2 exist within Type A, reflecting variations in antigen density. Blood type is determined by genetics and is relevant to transfusion compatibility and certain clinical considerations.

In psychology, Type A personality denotes a cluster of traits including competitiveness, time urgency, and hostility. The concept, introduced by Friedman and Rosenman in the 1950s, linked Type A behavior with a higher risk of coronary heart disease, though later research has contested a direct causal relationship and emphasized that health outcomes are influenced by multiple factors.

Other common uses include the USB Type-A connector, the standard rectangular plug found on many devices, and generic labeling in various technical and organizational typologies where Type A denotes a primary or original category alongside Type B and beyond.

In biology and taxonomy, the term type or type specimen is used to anchor the name of a species, with various labeling systems that may designate different specimens or references. The meaning of Type A, when encountered, depends on the specific field and context in which it is used.