marvellous vs phenomenal

marvellous and phenomenal both are adjectives.

Word	Noun	Adjective	Verb	Adverb
marvellous	No	Yes	No	No
phenomenal	No	Yes	No	No

As adjectives, marvellous and phenomenal are synonyms defined as:

marvellous and phenomenal: extraordinarily good or great; used especially as intensifiers

Other synonyms of marvellous include fantastic, grand, howling, marvelous, rattling, terrific, tremendous, wonderful, wondrous.

marvellous (adjective)	phenomenal (adjective)
extraordinarily good or great; used especially as intensifiers	of or relating to a phenomenon
too improbable to admit of belief	extraordinarily good or great; used especially as intensifiers
being or having the character of a miracle