seppuku vs hara-kiri

seppuku and hara-kiri both are nouns.

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

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

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

Other synonyms of seppuku include harakiri, harikari.

seppuku (noun)	hara-kiri (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