convulsion vs seizure

convulsion and seizure both are nouns.

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

As nouns, seizure is a hypernym of convulsion; that is, seizure is a word with a broader meaning than convulsion:

Other hypernyms of convulsion include ictus, raptus.

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