Eric Chang, The Only True God, pp 44-46.

As Trinitarians we argued that we are monotheists, not polytheists, because our faith is in one God in three Persons. We closed our eyes (and ears) to the fact which should have been perfectly obvious: if the Father is God, and the Son is God, and the Spirit is God, and all three are co-equal and co-eternal, then the conclusion is inescapable that there are three Gods. So how did we manage to maintain that we still believe in one God? There was only one way: the definition of the word ‘God’ had to be changed — from Person to a divine Substance (or Nature) in which the three Persons share equally…Trinitarians changed the Biblical concept of God by daringly introducing polytheism into the church under the guise of ‘monotheism.’ In so doing they changed the meaning of the word God.

Whatever other reasons there may have been for the church’s having gradually but steadily moved away from its original monotheism…Christ was now proclaimed to be God [and] God was now no longer one personal Being but a group of three co-equal Persons. This meant that the very meaning of the word ‘God’ had changed from being one divine Person into three divine Persons sharing one divine ‘substance’…Thus the Biblical proclamation fundamental to the Biblical faith in both the OT and the NT expressed clearly in the words:

Hear, O Israel, the LORD (Yahweh) our God, the LORD (Yahweh) is One (Deut. 6:4; Mark 12:29) was changed in essence to: Hear, O Church, the Lord your God is THREE.

Though deliberately changing the way the word ‘God’ is defined and understood is an extremely serious matter, the seriousness of the matter does not end there. What happens in the Trinitarian declaration is a flat contradiction of the divine revelation that Yahweh (the LORD) is ONE…One Being, one Entity, one Person, as is clearly seen in the Hebrew Bible; and it is no different in the New Testament…The fact is that Trinitarian ‘monotheism’ can only qualify as monotheism by changing the definition of the word ‘monotheism’. It is rather like saying that an angel is a human being by changing the meaning of the term ‘human being’ to include angels…This can hardly be considered acceptable to those, like Jews (and Muslims), who know that this kind of argumentation is a denial of the radical, uncompromising monotheism [of the scriptures].