I Thessalonians vs First Epistle to the Thessalonians

I Thessalonians and First Epistle to the Thessalonians both are nouns.

Word	Noun	Adjective	Verb	Adverb
I Thessalonians	Yes	No	No	No
First Epistle to the Thessalonians	Yes	No	No	No

As nouns, I Thessalonians and First Epistle to the Thessalonians are synonyms defined as:

I Thessalonians and First Epistle to the Thessalonians: a New Testament book containing Saint Paul's first epistle to the Thessalonians

Other synonyms of I Thessalonians include First Epistle of Paul the Apostle to the Thessalonians.

I Thessalonians (noun)	First Epistle to the Thessalonians (noun)
a New Testament book containing Saint Paul's first epistle to the Thessalonians	a New Testament book containing Saint Paul's first epistle to the Thessalonians