white alder vs sweet pepperbush

white alder and sweet pepperbush both are nouns.

Word	Noun	Adjective	Verb	Adverb
white alder	Yes	No	No	No
sweet pepperbush	Yes	No	No	No

As nouns, white alder and sweet pepperbush are synonyms defined as:

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

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

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