both different words were found used in john 1:1 .to me that indicates a difference between the two words that both translate to the word God or god . we have been told ,in English ,to use the upper case G when referring to the almighty God . to all other gods the lower case g is used . at the moment its a curiosity to me.
θεὸς and θεόν are the same word; the first is in the accusative case and the second in the nominative. The reason why the NWT falsely translates "God" and "a god," is
Joh 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. (ESV)
In the second clause, "and the Word was with God," it is important to note that in the Greek the article is present, so it literally reads, "the Word was with [the] God." So, God is a reference to someone other than the Word, at a minimum it is a reference to the Father.
When it comes to the last clause, "the Word was God," it is significant that "God"
doesn't have the article in the Greek, as it did in the preceding clause. If the article
had been present then "Word" and "God" become interchangeable— they would be one and the same—which is the error of Modalism/Oneness theology. Without the definite article, it can only mean either "a god" or be of a qualitative sense (having the qualities or nature of God).
Of course, the NWT uses this to mean that the word was "a god," but that is false, as that is polytheism. We can rule out "a god" immediately because of what God has already told us:
Deu 4:35 To you it was shown, that you might know that
the LORD is God; there is no other besides him.
…
Deu 4:39 know therefore today, and lay it to your heart, that
the LORD is God in heaven above and on the earth beneath;
there is no other.
Deu 6:4 “Hear, O Israel: The LORD our God, the LORD is one.
Deu 32:39 "'See now that I, even I, am he, and
there is no god beside me; I kill and I make alive; I wound and I heal; and there is none that can deliver out of my hand.
Isa 43:10 "You are my witnesses," declares the LORD, "and my servant whom I have chosen, that you may know and believe me and understand that I am he.
Before me no god was formed, nor shall there be any after me.
Isa 43:11 I, I am the LORD, and besides me there is no savior.
Isa 44:6 Thus says the LORD, the King of Israel and his Redeemer, the LORD of hosts: “
I am the first and I am the last; besides me there is no god.
Isa 44:7 Who is like me? Let him proclaim it. Let him declare and set it before me, since I appointed an ancient people. Let them declare what is to come, and what will happen.
Isa 44:8 Fear not, nor be afraid; have I not told you from of old and declared it? And you are my witnesses!
Is there a God besides me? There is no Rock; I know not any.”
…
Isa 44:24 Thus says the LORD, your Redeemer, who formed you from the womb: "I am the LORD,
who made all things, who alone stretched out the heavens, who spread out the earth by myself,
Isa 45:5
I am the LORD, and there is no other, besides me there is no God; I equip you, though you do not know me,
Isa 45:6 that people may know, from the rising of the sun and from the west, that
there is none besides me; I am the LORD, and there is no other.
…
Isa 45:18 For thus says
the LORD, who created the heavens (he is God!),
who formed the earth and made it (he established it; he did not create it empty, he formed it to be inhabited!): "
I am the LORD, and there is no other.
…
Isa 45:21 Declare and present your case; let them take counsel together! Who told this long ago? Who declared it of old? Was it not I, the LORD? And
there is no other god besides me, a righteous God and a Savior; there is none besides me.
Isa 45:22 "Turn to me and be saved, all the ends of the earth! For
I am God, and there is no other.
Isa 46:9 remember the former things of old; for
I am God, and there is no other; I am God, and there is none like me,
Isa 48:11 For my own sake, for my own sake, I do it, for how should my name be profaned?
My glory I will not give to another.
Isa 48:12 "Listen to me, O Jacob, and Israel, whom I called! I am he;
I am the first, and I am the last.
Isa 48:13 My hand laid the foundation of the earth, and my right hand spread out the heavens; when I call to them, they stand forth together.
(All ESV.)
Of course, that is repeated throughout the NT as well. So, we know without a doubt that there is only one God and no other actual living god that is in any way divine. That precludes the translation "a god." Therefore, it can only have a qualitative meaning, that is, that the Word was divine in nature, or deity. However, since there is only one God, it is rightly translated as "the Word was God."
John's grammar is very specific, to show that the Word is a divine person distinct from the Father, yet equal to him, being true deity, while at the same time avoiding such heresies as Modalism, Arianism, and polytheism.