estimation vs appraisal

estimation and appraisal both are nouns.

Word	Noun	Adjective	Verb	Adverb
estimation	Yes	No	No	No
appraisal	Yes	No	No	No

As nouns, appraisal is a hyponym of estimation; that is, appraisal is a word with a more specific, narrower meaning than estimation:

estimation: a judgment of the qualities of something or somebody
appraisal: an expert estimation of the quality, quantity, and other characteristics of someone or something

Other hyponyms of estimation include capitalisation, capitalization.

As nouns, estimation and appraisal are synonyms defined as:

estimation and appraisal: a document appraising the value of something (as for insurance or taxation)

Other synonyms of estimation include estimate.

estimation (noun)	appraisal (noun)
a judgment of the qualities of something or somebody	an expert estimation of the quality, quantity, and other characteristics of someone or something
an approximate calculation of quantity or degree or worth	the classification of someone or something with respect to its worth
the respect with which a person is held	a document appraising the value of something (as for insurance or taxation)
a document appraising the value of something (as for insurance or taxation)