Diverging from, or tributary to, a main stock, line, way, theme, etc.; as, a branch vein; a branch road or line; a branch topic; a branch store.(adjective)
source: webster1913
noun (n)
a division of some larger or more complex organization(noun.group)
Example: A branch of Congress.
Botany is a branch of biology.
The Germanic branch of Indo-European languages.