Mount Saint Helens vs Mt. St. Helens

Mount Saint Helens and Mt. St. Helens both are nouns.

Word	Noun	Adjective	Verb	Adverb
Mount Saint Helens	Yes	No	No	No
Mt. St. Helens	Yes	No	No	No

As nouns, Mount Saint Helens and Mt. St. Helens are synonyms defined as:

Mount Saint Helens and Mt. St. Helens: an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity

Other synonyms of Mount Saint Helens include Mount St. Helens.

Mount Saint Helens (noun)	Mt. St. Helens (noun)
an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity	an active volcano in the Cascade Range in southwestern Washington; erupted violently in 1980 after 123 years of inactivity