Crux vs Crux Australis

Crux and Crux Australis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Crux	Yes	No	No	No
Crux Australis	Yes	No	No	No

As nouns, Crux and Crux Australis are synonyms defined as:

Crux and Crux Australis: a small conspicuous constellation in the Southern Hemisphere in the Milky Way near Centaurus

Other synonyms of Crux include Southern Cross.

Crux (noun)	Crux Australis (noun)
a small conspicuous constellation in the Southern Hemisphere in the Milky Way near Centaurus	a small conspicuous constellation in the Southern Hemisphere in the Milky Way near Centaurus