thalweg vs boundary

thalweg and boundary both are nouns.

Word	Noun	Adjective	Verb	Adverb
thalweg	Yes	No	No	No
boundary	Yes	No	No	No

As nouns, boundary is a hypernym of thalweg; that is, boundary is a word with a broader meaning than thalweg:

thalweg: the middle of the chief navigable channel of a waterway that forms the boundary line between states
boundary: a line determining the limits of an area

Other hypernyms of thalweg include bound, edge.

thalweg (noun)	boundary (noun)
a line following the lowest points of a valley	the greatest possible degree of something
the middle of the chief navigable channel of a waterway that forms the boundary line between states	the line or plane indicating the limit or extent of something
	a line determining the limits of an area