Not part: “the Incarnation …does not mean that Jesus Christ is part God and part man, nor does it imply that He is the result of a confused mixture of the divine and the human.” (CCC 464)
There are various ways people understood Jesus in the early Church. A lot of this was worked out at the early ecumenical councils. Some examples of these errors are that Jesus was part God and part man, but the truth is that Jesus is fully God and fully man.
Assumed: "human nature was assumed, not absorbed" (GS 22)
The difference between assumed and absorbed is that assumed maintains his personal nature, while absorbed would mean his humanity would be lost within the Trinity in some kind of state of common unity which would be impersonal.