power shovel vs digger

power shovel and digger both are nouns.

Word	Noun	Adjective	Verb	Adverb
power shovel	Yes	No	No	No
digger	Yes	No	No	No

As nouns, power shovel and digger are synonyms defined as:

Other synonyms of power shovel include excavator, shovel.

power shovel (noun)	digger (noun)
a machine for excavating	a machine for excavating
	a laborer who digs