bathyal zone vs continental slope

bathyal zone and continental slope both are nouns.

Word	Noun	Adjective	Verb	Adverb
bathyal zone	Yes	No	No	No
continental slope	Yes	No	No	No

As nouns, bathyal zone and continental slope are synonyms defined as:

bathyal zone and continental slope: the steep descent of the seabed from the continental shelf to the abyssal zone

Other synonyms of bathyal zone include bathyal district.

bathyal zone (noun)	continental slope (noun)
the steep descent of the seabed from the continental shelf to the abyssal zone	the steep descent of the seabed from the continental shelf to the abyssal zone