Jehovah Witness try to invalidate the power of the testimony of the apostle John who wrote: «In the beginning was the Word, and the Word was with God... And the Word became flesh and dwelt among us» (John 1:1, 14) by suggesting that the passage should be translated «the word was a god» since the word «Theos» has no definite article in the Greek. However, please note that Greek grammar does not require a definite article before the word Theos for it to mean God, as is the case in John 1:6, 12, 13, 18. The comments for John 1 on the printed edition of the ESV Study Bible are very clear with this regard. Comments of the ESV Global Study Bible for John 1:1 available on line are a little let explicit and a little less extended on this question, but are still valuable.