arbor vs pergola

arbor and pergola both are nouns.

Word	Noun	Adjective	Verb	Adverb
arbor	Yes	No	No	No
pergola	Yes	No	No	No

As nouns, arbor and pergola are synonyms defined as:

Other synonyms of arbor include arbour, bower.

arbor (noun)	pergola (noun)
a framework that supports climbing plants	a framework that supports climbing plants
any of various rotating shafts that serve as axes for larger rotating parts
tree (as opposed to shrub)