emblem vs heraldry

emblem and heraldry both are nouns.

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

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

emblem: special design or visual object representing a quality, type, group, etc.
heraldry: emblem indicating the right of a person to bear arms

Other hyponyms of emblem include colophon, colors, colours, crest, Cross, device, flag, skull and crossbones, totem, totem pole.

emblem (noun)	heraldry (noun)
special design or visual object representing a quality, type, group, etc.	emblem indicating the right of a person to bear arms
a visible symbol representing an abstract idea	the study and classification of armorial bearings and the tracing of genealogies