In Christian usage, the Greek word hypostasis, the range of whose meanings is illustrated in Liddel and Scott's Greek Lexicon,[1] has a complicated and sometimes confusing history. Its basic meaning is "that which stands beneath". In Scriptures this seems roughly its meaning at Hebrews 1:3. Allied to this was its use for "basis" or "foundation" and hence also "confidence," e.g., in Hebrews 3:14 and 11:1 and 2 Corinthians 9:4 and 11:17.

In early Christian writers it is used to denote "being" or "substantive reality" and is not always distinguished in meaning from ousia (essence); it was used in this way by Tatian and Origen, and also in the anathemas appended to the Nicene Creed of 325. It was mainly under the influence of the Cappadocian Fathers that the terminology was clarified and standardized, so that the formula "Three Hypostases in one Ousia" came to be everywhere accepted as an epitome of the orthodox doctrine of the Holy Trinity. This consensus, however, was not achieved without some confusion at first in the minds of Western theologians, who had translated hypo-stasis as "sub-stantia" and understood the Eastern Christians, when speaking of three "Hypostases" in the Godhead, to mean three "Substances," i.e. they suspected them of Tritheism. But, from the middle of the fourth century onwards the word came to be contrasted with ousia and used to mean "individual reality," especially in the Trinitarian and Christological contexts. With regard to the doctrine of the Trinity, hypostasis is usually understood with a meaning akin to the Greek word prosopon, which is translated into Latin as persona and then into English as person. The Christian view of the Trinity is often described as a view of one God existing in three distinct hypostases/personae/persons.

Trinitarians defend their view of multiple hypostases in the single God by, among other things, appealing to Jewish pneumatology (the "Spirit of God" and "Spirit of the Lord"), and angelology (the "Angel of the Lord"); a study of Jewish conceptions of the prophetic "word of the Lord" which comes to the prophets, and by the authority of which they declared "thus says the Lord"; the New Testament's doctrine of the identity of Christ which developed after the resurrection, and the pattern of prayer, devotion, and theological apologetics exhibited in the early Church.