seal vs holdfast

seal and holdfast both are nouns.

Word	Noun	Adjective	Verb	Adverb
seal	Yes	No	Yes	No
holdfast	Yes	No	No	No

As nouns, holdfast is a hypernym of seal; that is, holdfast is a word with a broader meaning than seal:

seal: fastener consisting of a resinous composition that is plastic when warm; used for sealing documents and parcels and letters
holdfast: restraint that attaches to something or holds something in place

Other hypernyms of seal include fastener, fastening, fixing.

As nouns, holdfast is a hypernym of seal; that is, holdfast is a word with a broader meaning than seal:

Other hypernyms of seal include fastener, fastening, fixing.

seal (noun)	holdfast (noun)
any of numerous marine mammals that come on shore to breed; chiefly of cold regions	restraint that attaches to something or holds something in place
a device incised to make an impression; used to secure a closing or to authenticate documents
fastener consisting of a resinous composition that is plastic when warm; used for sealing documents and parcels and letters
fastener that provides a tight and perfect closure
a finishing coat applied to exclude moisture
an indication of approved or superior status
a stamp affixed to a document (as to attest to its authenticity or to seal it)
the pelt or fur (especially the underfur) of a seal

seal (verb)	holdfast (verb)
decide irrevocably
hunt seals
close with or as if with a seal
affix a seal to
make tight; secure against leakage
cover with varnish