Peloponnesus vs Peloponnese

Peloponnesus and Peloponnese both are nouns.

Word	Noun	Adjective	Verb	Adverb
Peloponnesus	Yes	No	No	No
Peloponnese	Yes	No	No	No

As nouns, Peloponnesus and Peloponnese are synonyms defined as:

Peloponnesus and Peloponnese: the southern peninsula of Greece; dominated by Sparta until the 4th century BC

Other synonyms of Peloponnesus include Peloponnesian Peninsula.

Peloponnesus (noun)	Peloponnese (noun)
the southern peninsula of Greece; dominated by Sparta until the 4th century BC	the southern peninsula of Greece; dominated by Sparta until the 4th century BC