Word and Son are words used to reference Jesus as a person of the Holy Trinity. Son is used because it shows relation of God but not the Godhead itself. So these are taken personally but not essentially. The Son to be called Word is proper because the Word is the emanation of the intellect of God and as it proceeds from the God in generation it becomes the Son as well; a Paternal relationship. The speaking of God infers creation and so it is proper that the Word would be used in relation to creatures as operation but not as nature.
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