Nissen hut vs field hut

Nissen hut and field hut both are nouns.

Word	Noun	Adjective	Verb	Adverb
Nissen hut	Yes	No	No	No
field hut	Yes	No	No	No

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

Nissen hut: a prefabricated hut of corrugated iron having a semicircular cross section
field hut: temporary military shelter

Other hypernyms of Nissen hut include army hut, hut.

Nissen hut (noun)	field hut (noun)
a prefabricated hut of corrugated iron having a semicircular cross section	temporary military shelter