pepper bush vs white alder

pepper bush and white alder both are nouns.

Word	Noun	Adjective	Verb	Adverb
pepper bush	Yes	No	No	No
white alder	Yes	No	No	No

As nouns, pepper bush and white alder are synonyms defined as:

pepper bush and white alder: shrub of eastern and southern coastal United States having beautiful racemes of spice-scented white flowers

Other synonyms of pepper bush include Clethra alnifolia, summer sweet, sweet pepperbush.

pepper bush (noun)	white alder (noun)
shrub of eastern and southern coastal United States having beautiful racemes of spice-scented white flowers	tree of western United States
	shrub of eastern and southern coastal United States having beautiful racemes of spice-scented white flowers