electric discharge vs electric arc

electric discharge and electric arc both are nouns.

Word	Noun	Adjective	Verb	Adverb
electric discharge	Yes	No	No	No
electric arc	Yes	No	No	No

As nouns, electric discharge and electric arc are synonyms defined as:

electric discharge and electric arc: electrical conduction through a gas in an applied electric field

Other synonyms of electric discharge include arc, discharge, spark.

electric discharge (noun)	electric arc (noun)
electrical conduction through a gas in an applied electric field	electrical conduction through a gas in an applied electric field