hara-kiri vs seppuku

hara-kiri and seppuku both are nouns.

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

As nouns, hara-kiri and seppuku are synonyms defined as:

hara-kiri and seppuku: ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society

Other synonyms of hara-kiri include harakiri, harikari.

hara-kiri (noun)	seppuku (noun)
ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society	ritual suicide by self-disembowelment on a sword; practiced by samurai in the traditional Japanese society