Lower California vs Baja California Peninsula

Lower California and Baja California Peninsula both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lower California	Yes	No	No	No
Baja California Peninsula	Yes	No	No	No

As nouns, Lower California and Baja California Peninsula are synonyms defined as:

Lower California and Baja California Peninsula: a mountainous peninsula on northwest Mexico

Other synonyms of Lower California include Baja California.

Lower California (noun)	Baja California Peninsula (noun)
a mountainous peninsula on northwest Mexico	a mountainous peninsula on northwest Mexico