\Hy*pos"ta*sis\, n.; pl. {Hypostases}. [L., fr. Gr. ?
subsistence, substance, fr. ? to stand under; ? under + ? to
stand, middle voice of ? to cause to stand. See {Hypo-}, and
{Stand}.]
1. That which forms the basis of anything; underlying
   principle; a concept or mental entity conceived or treated
   as an existing being or thing.
2. (Theol.) Substance; subsistence; essence; person;
   personality; -- used by the early theologians to denote
   any one of the three subdivisions of the Godhead, the
   Father, Son, and Holy Spirit.
Note: The Council of Alexandria (a. d. 362) defined
      hypostasis as synonymous with person. --Schaff-Herzog.
3. Principle; an element; -- used by the alchemists in
   speaking of salt, sulphur, and mercury, which they
   considered as the three principles of all material bodies.
4. (Med.) That which is deposited at the bottom of a fluid;
   sediment.