imperial decree vs fiat

imperial decree and fiat both are nouns.

Word	Noun	Adjective	Verb	Adverb
imperial decree	Yes	No	No	No
fiat	Yes	No	No	No

As nouns, fiat is a hypernym of imperial decree; that is, fiat is a word with a broader meaning than imperial decree:

imperial decree: a decree issued by a sovereign ruler
fiat: a legally binding command or decision entered on the court record (as if issued by a court or judge)

Other hypernyms of imperial decree include decree, edict, order, rescript.

imperial decree (noun)	fiat (noun)
a decree issued by a sovereign ruler	a legally binding command or decision entered on the court record (as if issued by a court or judge)