William Barclay on John 1:1c

. . . John says that the word was God. This is a difficult saying for us to understand, and it is difficult because Greek, in which John wrote, had a different way of saying things from the way in which English speaks. When Greek uses a noun it almost always uses the definite article with it. The Greek for God is theos and the definite article is ho. When Greek speaks about God it does not simply say theos; it says ho theos. Now when Greek does not use the definite article with a noun that noun becomes much more like an adjective. John did not say that the word was ho theos; that would have been to say that the word was identical with God. He said that the word was theos—without the definite article—which means that the word was, we might say, of the very same character and quality and essence and being as God. When John said the word was God he was not saying that Jesus was identical with God; he was saying that Jesus was so perfectly the same as God in mind, in heart, in being that in him we perfectly see what God is like. (William Barclay, The Gospel of John, volume 1: Chapters 1-7 [rev ed.; The Daily Study Bible; Edinburgh: The Saint Andrew Press, 1975], 39)