say-so vs pronouncement

say-so and pronouncement both are nouns.

Word	Noun	Adjective	Verb	Adverb
say-so	Yes	No	No	No
pronouncement	Yes	No	No	No

As nouns, say-so and pronouncement are synonyms defined as:

Other synonyms of say-so include dictum.

say-so (noun)	pronouncement (noun)
the power or right to give orders or make decisions	an authoritative declaration
an authoritative declaration
one chap's arbitrary assertion