megacycle per second vs megacycle

megacycle per second and megacycle both are nouns.

Word	Noun	Adjective	Verb	Adverb
megacycle per second	Yes	No	No	No
megacycle	Yes	No	No	No

As nouns, megacycle per second and megacycle are synonyms defined as:

Other synonyms of megacycle per second include Mc, megahertz, MHz.

megacycle per second (noun)	megacycle (noun)
one million periods per second	one million periods per second