ERA vs earned run average

ERA and earned run average both are nouns.

Word	Noun	Adjective	Verb	Adverb
ERA	Yes	No	No	No
earned run average	Yes	No	No	No

As nouns, ERA and earned run average are synonyms defined as:

ERA and earned run average: (baseball) a measure of a pitcher's effectiveness; calculated as the average number of earned runs allowed by the pitcher for every nine innings pitched

ERA (noun)	earned run average (noun)
(baseball) a measure of a pitcher's effectiveness; calculated as the average number of earned runs allowed by the pitcher for every nine innings pitched	(baseball) a measure of a pitcher's effectiveness; calculated as the average number of earned runs allowed by the pitcher for every nine innings pitched