heraldry vs blazon

heraldry and blazon both are nouns.

Word	Noun	Adjective	Verb	Adverb
heraldry	Yes	No	No	No
blazon	Yes	No	Yes	No

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

Other hyponyms of heraldry include armorial bearing, bearing, charge, heraldic bearing, arms, blazonry, coat of arms.

heraldry (noun)	blazon (noun)
emblem indicating the right of a person to bear arms	the official symbols of a family, state, etc.
the study and classification of armorial bearings and the tracing of genealogies

heraldry (verb)	blazon (verb)
	decorate with heraldic arms