verb / noun
annex
AN-eks/ˈæneks/
To add something as an attached part of a larger whole.
The official annexes the neighboring territory, extending the larger jurisdiction's boundary.

Etymology
The underlying image is tying something to something else. In territorial use, that connection becomes formal incorporation under another authority, rather than merely physical attachment.
In context
In March 1778, 16 New Hampshire towns requested Vermont annex them, which Vermont agreed to do after a referendum.
More examples
- The agreement includes the technical tables in an annex.
- The empire sought to annex the neighboring territory.
- We annexed the supporting documents to the final report.
Forms
annex · annexes · annexed · annexing
annexation noun — The act of adding territory to a larger entity.
Similar words
- append
- Usually means adding material to the end of a document.
- incorporate
- Emphasizes making something part of a whole rather than attaching it.