suicide vs hara-kiri

suicide and hara-kiri both are nouns.

Word	Noun	Adjective	Verb	Adverb
suicide	Yes	No	No	No
hara-kiri	Yes	No	No	No

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

suicide: the act of killing yourself
hara-kiri: 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, harakiri, harikari, seppuku, suttee.

suicide (noun)	hara-kiri (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