gigacycle per second vs gigahertz

gigacycle per second and gigahertz both are nouns.

Word	Noun	Adjective	Verb	Adverb
gigacycle per second	Yes	No	No	No
gigahertz	Yes	No	No	No

As nouns, gigacycle per second and gigahertz are synonyms defined as:

Other synonyms of gigacycle per second include Gc, GHz, gigacycle.

gigacycle per second (noun)	gigahertz (noun)
1,000,000,000 periods per second	1,000,000,000 periods per second