What is Annex?

Legal Definition
To add to; to unite; to attach one thing permanently to another. The word expresses the idea of joining a smaller or subordinate thing with another, larger or of higher importance. In the la"w relating to fixtures, the expression "annexed to the freehold" means fastened to or connected with it; mere juxtaposition, or the laying of an object, however heavy, on the frcehold, does not amount to annexation. Merritt v. Judd, 14 Cal. 64.
-- Black's Law Dictionary