Instead of this the Greeks use πρόσωπον/face/mask/character, τρόπον ὑπάρξεως, manner/temper of existence, ὑφιστάμενον/subsistence, ὑπόστασιν/hypostasis/substance: see SUICERUS’ Thesaurum ecclesiasticum on the words Πρόσωπον and Ὑπόστασις. Expositione Fidei, in JUSTIN MARTYR’S operibus, page 373, Οὐ ταὐτὸν οὖν τῷ πατρὶ ὁ υἱὸς καὶ τὸ πνεῦμα τὸ ἅγιον· ὅτι τὸ μὲν ἀγέννητον καὶ γεννητὸν καὶ ἐκπορευτὸν, οὐκ οὐσίας ὀνόματα, ἀλλὰ τρόποι ὑπάρξεως· ὁ δὲ τρόπος τῆς ὑπάρξεως, τοῖς ὀνόμασι χαρακτηρίζεται τούτοις. ἡ δὲ τῆς οὐσίας δήλωσις, τῇ Θεὸς ὀνομασίᾳ σημαίνεται· ὡς εἶναι τὴν διαφορὰν τῷ πατρὶ πρὸς τὸν υἱὸν καὶ τὸ πνεῦμα, κατὰ τὸν τῆς ὑπάρξεως τρόπον· τὸ δὲ ταὐτὸν, κατὰ τὸν τῆς οὐσίας λόγον, the Son and the Holy Spirit are not identical with the Father: for unbegotten, begotten, and proceeding are not designations of being/substance, but guises/characters of substance: but the guise/character of the substance is characterized by those designations: But the manifestation of the being is indicated by the designation God: so that the distinction between the Father and the Son and Spirit is according to the guise/ character of the substance: but they are identical with respect to being. The same in Questionibus et Responsionibus ad Orthodoxos, question CXXIX, page 480, Διαφορὰ δέ ἐστιν ἐν μὲν τῇ ἁγιᾳ τριάδι κατὰ τρόπους τῆς τῶν ὑποστάσεων ὑπάρξεως, there is a distinction in the holy triad according to the guises/characters of the substance of the hypostases. JOHN OF DAMASCUS’ “Dialectic”, chapter LXVI, page 673, Ἰστέον δὲ ὡς αὐτῆς τῆς ἁγίας τριάδος ὑποστασίς ἐστιν ὁ ἄναρχος τρόπος τῆς ἑκάστου ἀϊδίου ὑπάρξεως, but it is to be observed that in the Holy Triad a hypostasis is the timeless mode/guise/character of each eternal existence.
With the term ὑποστάσεως/hypostasis found in Hebrews 1:3. Of course, in that place Paul calls the Son the character, or express image, not simply of the Father’s Essence, for the Son has exactly the same Essense as the Father; nor of His Personality in the abstract, for the particular Mode of subsistence is so proper to each of the Persons, that one Person does not resemble another in this, but that especially in this matter they are distinguished from each other: but the Son is the character/image of the Father’s Person in the concrete, most perfectly resembling the Father with respect to Essence and Essential Attributes, because of course they have these in common among themselves; compare TRIGLAND’S in his Dissertationum Sylloge, Dissertation on Hebrews 1:3, § 16, 17, Pages 281-283: in the same sense the Son is called εἰκὼν τοῦ Θεοῦ τοῦ ἀοράτου, the image of the invisible God, Colossians 1:15, although otherwise perhaps ὑπόστασις/hypostasis and ὑφιστάμενον/subsistence, no less than personalitas/personality and persona/person, are able to be distinguished as abstract and concrete.
Now, the Greek Fathers made use of a diverse senses of the term ὑπόστασις/hypostasis, sometimes more broadly for the very Substance of a thing, and the divine Essence, as it is in ATHANASIUS’ Epistola ad Antiochenses, opera, tome I, page 577, Ὑπόστασιν μὲν λέγομεν, ἡγούμενοι ταὐτὸν εἶναι, εἰπεῖν ὑπόστασιν καὶ οὐσίαν, we use ὑπόστασις/hypostasis, supposing it to be the same thing as οὐσία/ousia/ essence: and in his Epistola ad Africanos, opera, tome I, pages 934, 935, Ἡ δὲ ὑπόστασις οὐσία ἐστὶ, καὶ οὐδὲν ἄλλο σημαινόμενον ἔχει, ἢ αὐτὸ τὸ ὂν· ἡ γὰρ ὑπόστασις καὶ ἡ οὐσία, ὕπαρξίς ἐστιν· ἔστι γὰρ καὶ ὑπάρχει, ὑπόστασις/hypostasis is οὐσία/ousia/being/ substance, and has no other signification except being: for ὑπόστασις/ hypostasis and οὐσία/ousia/essence is existence; for it is and exists. Whence in the Synod of Serdica held in the year 347 it was asserted, that it belonged to the heretics to assert that there are three Hypostases, but it belonged to the Catholic to assert only one. But now they more narrowly make use of the same term for a subsistence and person; hence at the Council of Alexandria, held in the year 362 with Athanasius presiding, was composed a quarrel that had long exercised the Western and Eastern Churches, whether it was to be said that there is one Hypostasis or three Hypostases in the Holy Trinity? Thus was established the distinction between οὐσία/ousia/essence and ὑπόστασις/hypostasis, so that, if ὑπόστασις/hypostasis is taken for τρόπῳ ὑπάρξεως, manner/temper of existence, or mode of subsistence, then there are three ὑποστάσεις/hypostases, against Sabellius; otherwise, there is one οὐσία/ousia/essence/substance: see SUICERUS’ Thesaurum ecclesiasticum on the word Ὑπόστασις; SPANHEIM’S Historiam Ecclesiasticam, Century IV, chapter XI, column 910; BUDDEUS’ Theologiæ Dogmaticæ, book II, chapter I, § 51, tome I, pages 382-384. Whence, as AUGUSTINE testifies in book V of Concerning the Trinity, chapter VIII, opera, tome 8, column 594, they were accustomed to say μίαν οὐσίαν, τρεῖς ὑποστάσεις, one essence, three hypostases. While in the place of οὐσίᾳ/ousia/essence they also sometimes use φύσιν/phusis/essence, as it is, for example, in AMPHILOCHIUS’ Jambis ad Seleucum, verses 193-199.
Μονὰς γάρ ἐστι καὶ τριὰς [ἡ] ἀΐδιος,
Πατὴρ σὺν υἱῷ καὶ πανάγνῳ (or παναγίῳ) πνεύματι,
Τριὰς προσώποις εὐκρινὴς, μονὰς φύσει.
Μήτ᾽ οὖν ἀριθμῷ συγχέῃς ὑποστάσεις,
Μήτ᾽ αὖ Θεὸν σὺ προσκυνῶν τέμῃς φύσιν.
Μία τριὰς γὰρ, εἶς Θεὸς παντοκράτωρ·
Τουτέστι λεπτὸν εὐσεβὲς μυστήριον.
For the eternal Trinity is a unity,
The Father with the Son and the all-holy Spirit;
The Trinity, rightly distinguished in persons, is a unity.
So, neither should you numerically confound the hypostases;
Nor should you as a worshipper of God divide His essence.
For there is one Trinity, one God almighty:
That is a subtle mystery of religion.
In the place of which οὐσίᾳ/ousia/essence is found again in the same sense, AMPHILOCHIUS’ Jambis ad Seleucum, verses 206, 207, in which it is asserted concerning the error of Sabellius and Arius,
Ὁ μὲν, προσώπων συγχέων ὑπόστασιν,
Ὁ δὲ οὖν, μερίζων δυσσεβῶς τὴν οὐσίαν.
The one confuses the subsistences of the persons;
The other then impiously divides the essence.
In which place, moreover, this exceedingly useful admonition is subjoined, verses 208-213.
Σὺ δ᾽ ἀκλινῶς φύλασσε τὴν μέσην ὁδὸν,
Ὡς χρὴ, διαιρῶν· καὶ συνάπτων, ὡς θέμις.
Συνάπτεται γὰρ ἡ τριὰς ἀσυγχύτως,
Ὥσπερ κ᾽ ἀτμήτως ἡ μονὰς χωρίζεται·
Ἡ γὰρ φύσις, ἄτμητος· αἱ δ᾽ ὑποστάσεις,
Ἀεὶ μένουσι παντελῶς ἀσύγχυτοι.
But keep thou unswervingly to the middle way,
When necessary, dividing; conjoining, when right.
For the Trinity is united without confusion,
As also the Unity is distinguished without division:
For the nature/essence is indivisible; but the hypostases
Ever remain absolutely conjoind.
But, as the Greeks also understood ὑπόστασιν/hypostasis of Essence as Substance, so also the Latins sometimes used Substance for Person, in which sense HILARY, libro de Synodis, acknowledges three Substance in the Divinity, chapter XXXII, column 1170: “Therefore, the synod of the saints assembled in Antioch, desiring to destroy that impiety, which would evade the truth/reality of the Father, of the Son, and of the Holy Spirit, as a mere number of names; so that, with no personal/subsisting cause of each name, the threefold pronouncement obtains union under the falsehood of names, and the Father alone, both one and the same, and Himself, has the name both of the Holy Spirit and of the Son: therefore, the synod said that there are three Substance, referring to the persons of those subsisting by substances, not separating the substance of the Father and the Son by a diversity of dissimilar essence:” on which place consult the Notas. Others, on the other hand, admit only one Substance in the Deity, and expressly deny that there are trhee; for example, TERTULLIAN, adversus Praxeam, chapter II, page 501, and AUGUSTINE, book V de Trinitate, chapter IX, column 594, tome 8, since these of course take Substance for Essence and Nature. TERTULLIAN in that passage says that God is one through unity of substance: but Three, the Father, the Son, and the Holy Spirit, not with respect to substance, but with respect to form: but of one substance, and of one glory, and of one power, because He is one God. Likewise, AUGUSTINE in the passage cited, “Our custom of speech has already obtained, that what is understood when we say substance, this is understood when we say essence: we dare not say one essence, three substances; but one essence, or substance, but three persons; as many Latin, treating of these things and worthy of authority, have spoken, since they did not find another more apt manner of speaking, whereby they might relate in words what they were understanding without words.” JEROME, Epistola ad Damasum, opera, tome 2, pages 131, 132, acknowledges three divine Persons subsisting: but he maintains that three hypostases are no more prediacted of God than three substances, adding for a reason: The entire school of secular letters says that hypostasis is nothing other than ousia. On which things see CALVIN’S ἐπίκρισιν of his Institutes of the Christian Religion, book I, chapter XIII, § 5, where among other things he observes that JEROME asserts with insufficient modesty that in all the profane schools οὐσίαν/ousia/ essence is nothing other than hypostasis, which, he adds, is everywhere refuted by common and well-known usage: commending AUGUSTINE as more modest and more refined in his judgment concering the use of the word Hypostasis among the Greeks. And so Substance and Subsistence are distinguished from each other τεχνικῶς/technically and in use, so that the former denotes Essence, the thing subsisting; but the latter the person or personality, the mode in which a thing subsists: otherwise, according to their origins Substance and Subsistence agree equally in signification, as do substare and subsistere, whence they are derived: compare TRIGLAND’S Dissertationum Syllogen, Dissertation on Hebrews 1:3, § 15, 16, pages 277-282. But Subsistence thus differs from Existence, inasmuch as Existence expresses that a thing apart from its causes actually is in the nature of things, which is resolved into accidental properties and Substances; but Subsistence denotes the mode proper to Substances. Yet not always to rational Substances alone: but Subsistence and Personality are distinguished more broadly and more narrowly, in the same way as Subsistence and Person, the former of which is common to brutes, the latter proper to rational Substances. On these things, which I have hitherto taught in this § concerning the various terms customarily used in the explication of this doctrine, and their diverse senses, consult at great length PETAVIUS’ Dogmata theologica, tome 2, book IV, chapters I-IV, VII.
But here Person generally denotes an Intelligent, Individual, and Incommunicable Substance; in which manner Subsistence is regarded concretely with Essence. Somewhat more fully in MELANCHTHON, Locis Communibus on definitionibus Theologicis; POLANUS, Syntagmate Theologiæ, book III, chapter VI, page 216, column 1E; and URSINUS, Explicationum Catecheticarum, on question XXV, page 172: by whom an Individual subsisting, living, intelligent, incommunicable, not sustained by another, nor part of another is called a Person. When an Individual not sustained by another is called a Person, by these words the Personality of the human Nature of Christ is denied: when it is added, nor part of another, thus the human soul and body, although they exist separately after death, are denied to be Subsistences or Persons, since Communicability remains in them, as they will be united with one another again in the Resurrection, that they might constitute one Subsistence, to which they are determined as parts; on the other hand, a Person is an Incommunicable Individual. In which sense the Greek word πρόσωπον/face/person also occurs in the writings of Paul, 2 Corinthians 1:11, ἐκ πολλῶν προσώπων, by the means of many persons: compare PETAVIUS’ Dogmata theologica, tome 2, book IV, chapters VII-XI. But the consideration of Personality in the abstract, or of τρόπου ὑπάρξεως, the manner/temper of existence, Subsistence considered with the precision of Essense, is another thing.
 John Caspar Suicer (1620-1684) was a Swiss theologian and philologist. He studied at Saumur and Montauban, and served as Professor of Hebrew and Greek at the University of Zurich (1660). His Thesaurus ecclesiasticus was invaluable in the study of the Greek Fathers, shedding light upon words and expressions untreated by lexicographers.
 From The Fountain of Wisdom.
 Hebrews 1:3: “Who being the brightness of his glory, and the express image of his person (καὶ χαρακτὴρ τῆς ὑποστάσεως αὐτοῦ), and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high…”
 Jacobus Trigland the Younger (1652-1705) was a Dutch Reformed Theologian. Beginning in 1686, he served as Professor of Theology at Leiden.
 The Council of Serdica (in modern Bulgaria), composed of one hundred and seventy bishops, was convened to resolve the Arian crisis.
 Sabellius (flourished 215) taught that God was a single person, who manifested Himself in three modes (Father, Son, and Spirit) successively. Both Tertullian and Hippolytus of Rome vigorously opposed Sebellius’ anti-Trinitarian Modalism.
 Arius (c. 250-336) was a presbyter of the church in Alexandria, Egypt. He denied the Son to be of one substance, and co-equal Deity, with the Father. His views precipitated the Arian controversy, and led to the calling of the First Ecumenical Council at Nicea (325).
 Both of which mean to stand under.
 Denis Petau (1583-1652) was a French Jesuit churchman and scholar.
 Amandus Polanus (1561-1610) was a German Reformed theologian, and an important figure in the early development of Reformed Scholasticism. He served as Professor of Old Testament at Basel (1596-1610).
 Zacharias Ursinus (1534-1583) was a German Reformed theologian. He was a leader of the Reformation in the Palatinate, and served at the University of Heidelberg. He was involved in the composition of the Heidelberg Catechism.