A group of people authorized to act as a single entity (legally a person) and recognized as such in law. Corporations include companies, associations, firms, partnerships, societies, and joint stock companies, as well as Human beings.  They all have the constitutional guarantees of equal protection, and due process of law. 
Corporation 15c., "persons united in a body for some purpose, legally authorized entity" is from 1610s. 
13c., from "human being. In person "by bodily presence" is from 1560s. Person-to-person first recorded 1919, originally of telephone calls.