You will recall from an earlier posting that in Eastern Orthodoxy, the Evangelist John is commonly called John the Theologian. Icons of him are very common, and so is the text one usually finds on the book he holds, whether written in Greek or in Church Slavic.
Here is a Greek example from the end of the 14th century:
Here is a closer view of the text:
It is slightly worn, but we can easily emend it:
You will note the common abbreviations:
ΘC with a horizontal line above it for ΘΕΟC/Theos, “god.”
ΘΝ with a horizontal line above it for ΘΕΟΝ/Theon, “God” in the accusative form.
This is such a common text in icons and so frequently used a phrase in Christianity that everyone interested in icons should know it in Greek, at least as it is found in John 1:1-5. The portion used in the above icon text is in bold type here:
Ἐν ἀρχῇ ἦν ὁ λόγος, καὶ ὁ λόγος ἦν πρὸς τὸν θεόν, καὶ θεὸς ἦν ὁ λόγος. 2 οὗτος ἦν ἐν ἀρχῇ πρὸς τὸν θεόν. 3 πάντα δι’ αὐτοῦ ἐγένετο, καὶ χωρὶς αὐτοῦ ἐγένετο οὐδὲ ἕν. ὃ γέγονεν 4 ἐν αὐτῷ ζωὴ ἦν, καὶ ἡ ζωὴ ἦν τὸ φῶς τῶν ἀνθρώπων· 5 καὶ τὸ φῶς ἐν τῇ σκοτίᾳ φαίνει, καὶ ἡ σκοτία αὐτὸ οὐ κατέλαβεν.
En arkhe en ho logos, kai ho logos en pros ton Theon, kai theos en ho logos. Houtos en en arkhe pros to Theon. Panta di autou egeneto kai khoris autou egeneto oude hen. Ho gegonen en auto zoe en, kai he zoe en to phos ton anthropon. Kai to phos en te skotia phainei, ka he skotia auto ou katelaben.
“In [the] beginning was the Word/Reason, and the Word/Reason was with [the] God, and god was the Word/Reason. All through him came-to-be, and without him nothing came-to-be that has become. In him life was [or, depending on punctuation, ‘That which came to be in him was life’], and [the] life was the light of [the] men. And the light in the darkness shines, and the darkness has not overcome/taken/understood it.”
Huge amounts of ink have flowed through history on both the proper translation and the interpretation of this. “Logos” — ordinarily translated as “Word,” was actually a common term in Greek philosophy, used more in the sense of “Reason” as the reasoned order behind the universe. Philo of Alexandria — influenced by Greek philosophy — used it to refer to the divine Reason of God — an emanation of the invisible and hidden God through which he acts in the material universe — a “second god,” as Philo called it/him. This is the usage adopted in the Gospel called “of John,” saying essentially that this Reason was in the beginning, it was with God, and it was theos — that is, god by nature — divine. Theos indicates here the nature of the Logos, just as we would say of a person, “He is man, not animal.” In the same sense the Logos is god by nature. The Greek is deliberately ambiguous, to indicate a distinction of this Logos from the hidden God.
Of course this grammatical ambiguity has resulted in endless theological bickering over the centuries as to precisely in what sense Jesus as Logos is theos, — and it continues to this day among Christian denominations.
Fortunately, all we need worry about is learning to recognize this common inscription on the book held in icons of John.