seizure vs convulsion

seizure and convulsion both are nouns.

Word	Noun	Adjective	Verb	Adverb
seizure	Yes	No	No	No
convulsion	Yes	No	No	No

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

Other hyponyms of seizure include focal seizure, raptus hemorrhagicus, absence, absence seizure.

seizure (noun)	convulsion (noun)
the taking possession of something by legal process	a physical disturbance such as an earthquake or upheaval
the act of forcibly dispossessing an owner of property	violent uncontrollable contractions of muscles
the act of taking of a person by force	a sudden uncontrollable attack
a sudden occurrence (or recurrence) of a disease	a violent disturbance