power of appointment vs say-so

power of appointment and say-so both are nouns.

Word	Noun	Adjective	Verb	Adverb
power of appointment	Yes	No	No	No
say-so	Yes	No	No	No

As nouns, say-so is a hypernym of power of appointment; that is, say-so is a word with a broader meaning than power of appointment:

power of appointment: authority given (in a will or deed) by a donor to a donee to appoint the beneficiaries of the donor's property
say-so: the power or right to give orders or make decisions

Other hypernyms of power of appointment include authorisation, authority, authorization, dominance, potency.

power of appointment (noun)	say-so (noun)
authority given (in a will or deed) by a donor to a donee to appoint the beneficiaries of the donor's property	the power or right to give orders or make decisions
	an authoritative declaration
	one chap's arbitrary assertion