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.
⇒ 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.
© Webster 1913.