past simple vs simple past

past simple and simple past both are nouns.

Word	Noun	Adjective	Verb	Adverb
past simple	Yes	No	No	No
simple past	Yes	No	No	No

As nouns, past simple and simple past are synonyms defined as:

past simple and simple past: the form of a verb used to describe an action that happened before the present time and is no longer happening.

past simple (noun)	simple past (noun)
the form of a verb used to describe an action that happened before the present time and is no longer happening.	the form of a verb used to describe an action that happened before the present time and is no longer happening.