Jehovah’s Witnesses are famous for mistranslating John 1:1. They argue that the verse identifies Jesus as a god rather than as God Himself. Andreas Kostenberger, in The Gospels and Acts (The Holman Apologetics Commentary on the Bible), explains why their translation is incorrect.

Interestingly, around 1950 there was a change in how Jehovah’s Witnesses dealt with this verse. Before 1950, they carried a copy of the American Standard Version of the Bible. However, the problem they faced was that the ASV rendered verse 1 accurately with the phrase ‘the Word was God.’ In an effort to resolve the difficulty this rendering posed for its theology, the Watchtower Society (the Jehovah’s Witnesses’ publishing group) issued its own translation of the Bible, which rendered the verse as ‘the Word was a god’ (Reed 1986, 71). However, there are several reasons why this translation is inaccurate.

First, John, as a monotheistic Jew, would not have referred to another person as ‘a god.’ The Jews had no place for demigods in their belief system.

Second, if John had placed a definite article before theos, he would have abandoned the distinction between the two persons he established in the previous clause (‘the Word was with God’).

Third, the view defended by Jehovah’s Witnesses misunderstands Greek syntax. It is common in Greek for a predicate noun to be specific without having an article. For example, later in this chapter reference is made to Nathanael’s confession of Jesus, ‘you are the King of Israel’ (1: 49), with no article being before ‘King’ in the Greek (for other NT examples of this construction, see 8: 39; 17: 17; Rom 14: 17; Gal 4: 25; Rev 1: 20). From these examples, it is clear that the lack of an article in Greek does not necessarily imply indefiniteness (‘a’ god).

Finally, John could have used the word theios if he were simply trying to say that Jesus was ‘divine’ (i.e., that he had God-like qualities) rather than being God himself. The anarthrous (article-less) theos is most likely used to explain that Jesus ‘shared the essence of the Father though they differed in person’ (Wallace 1996, 269). As D. A. Carson explains, ‘In fact, if John had included the article, he would have been saying something quite untrue. He would have been so identifying the Word with God that no divine being could exist apart from the Word. In that case, it would be nonsense to say (in the words of the second clause of this verse) that the Word was with God.’