Greenwich Mean Time vs UT1

Greenwich Mean Time and UT1 both are nouns.

Word	Noun	Adjective	Verb	Adverb
Greenwich Mean Time	Yes	No	No	No
UT1	Yes	No	No	No

As nouns, Greenwich Mean Time and UT1 are synonyms defined as:

Greenwich Mean Time and UT1: the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

Other synonyms of Greenwich Mean Time include GMT, Greenwich Time, universal time, UT.

Greenwich Mean Time (noun)	UT1 (noun)
the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere	the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere