Mt. St. Helens vs Mount St. Helens

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

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

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

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

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

Mt. St. Helens (noun)	Mount 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