noun
decapitation (as a punishment)
Refers specifically to execution by beheading, often in historical or legal contexts.
斬首刑は、かつて多くの国で行われていた刑罰だ。
Decapitation was a punishment once carried out in many countries.
打ち首 is a more colloquial or historical term for beheading, often used in period dramas, whereas 斬首刑 is a formal legal term.
Compound of 斬首 (ざんしゅ, 'beheading') and 刑 (けい, 'punishment'). The exact historical derivation is uncertain, but the term is a straightforward Sino-Japanese legal compound.