The Holy Trinity

By definition, The word Trinity comes from a union of two words, Tri, which means three and the word Unity. In other words, it means a union of three. Mainstream Christianity teaches that there exists a Father, a Son and a Holy Spirit. All combine to make only one God. The Apostle John states, at John 17:3, that our salvation depends on knowing God. But, oddly enough, though he mentions that we must know the Son, he makes no mention of knowing the Holy Spirit.