suicide vs seppuku

suicide and seppuku both are nouns.

Word	Noun	Adjective	Verb	Adverb
suicide	Yes	No	No	No
seppuku	Yes	No	No	No

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

suicide: the act of killing yourself
seppuku: ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society

Other hyponyms of suicide include assisted suicide, felo-de-se, hara-kiri, harakiri, harikari, suttee.

suicide (noun)	seppuku (noun)
the act of killing yourself	ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society
a person who kills himself intentionally