What's the difference between advene and superadd?

Advene

Definition:

• (v. i.) To accede, or come (to); to be added to something or become a part of it, though not essential.

Example Sentences:

Superadd

Definition:

• (v. t.) To add over and above; to add to what has been added; to annex, as something extrinsic.

Example Sentences: