field marshal vs marshall

field marshal and marshall both are nouns.

Word	Noun	Adjective	Verb	Adverb
field marshal	Yes	No	No	No
marshall	Yes	No	No	No

As nouns, marshall is a hypernym of field marshal; that is, marshall is a word with a broader meaning than field marshal:

Other hypernyms of field marshal include marshal.

field marshal (noun)	marshall (noun)
an officer holding the highest rank in the army	a law officer having duties similar to those of a sheriff in carrying out the judgments of a court of law
	(in some countries) a military officer of highest rank