affidavit vs legal document

affidavit and legal document both are nouns.

Word	Noun	Adjective	Verb	Adverb
affidavit	Yes	No	No	No
legal document	Yes	No	No	No

As nouns, legal document is a hypernym of affidavit; that is, legal document is a word with a broader meaning than affidavit:

affidavit: written declaration made under oath; a written statement sworn to be true before someone legally authorized to administer an oath
legal document: (law) a document that states some contractual relationship or grants some right

Other hypernyms of affidavit include instrument, legal instrument, official document, testimony.

affidavit (noun)	legal document (noun)
written declaration made under oath; a written statement sworn to be true before someone legally authorized to administer an oath	(law) a document that states some contractual relationship or grants some right