emblem vs ensign

emblem and ensign both are nouns.

Word	Noun	Adjective	Verb	Adverb
emblem	Yes	No	No	No
ensign	Yes	No	No	No

As nouns, ensign is a hyponym of emblem; that is, ensign is a word with a more specific, narrower meaning than emblem:

emblem (noun)	ensign (noun)
special design or visual object representing a quality, type, group, etc.	colors flown by a ship to show its nationality
a visible symbol representing an abstract idea	an emblem flown as a symbol of nationality
	a person who holds a commissioned rank in the United States Navy or the United States Coast Guard; below lieutenant junior grade