cotton-seed tree vs shrub

cotton-seed tree and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
cotton-seed tree	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of cotton-seed tree; that is, shrub is a word with a broader meaning than cotton-seed tree:

cotton-seed tree: a shrub of salt marshes of eastern and south central North America and West Indies; fruit is surrounded with white plumelike hairy tufts
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of cotton-seed tree include bush.

cotton-seed tree (noun)	shrub (noun)
a shrub of salt marshes of eastern and south central North America and West Indies; fruit is surrounded with white plumelike hairy tufts	a low woody perennial plant usually having several major stems