yucca vs shrub

yucca and shrub both are nouns.

Word	Noun	Adjective	Verb	Adverb
yucca	Yes	No	No	No
shrub	Yes	No	No	No

As nouns, shrub is a hypernym of yucca; that is, shrub is a word with a broader meaning than yucca:

yucca: any of several evergreen plants of the genus Yucca having usually tall stout stems and a terminal cluster of white flowers; warmer regions of North America
shrub: a low woody perennial plant usually having several major stems

Other hypernyms of yucca include bush.

yucca (noun)	shrub (noun)
any of several evergreen plants of the genus Yucca having usually tall stout stems and a terminal cluster of white flowers; warmer regions of North America	a low woody perennial plant usually having several major stems