noun
A formal agreement to stop fighting, typically temporary. Used in historical or political contexts.
第一次世界大戦のアーミスティスは1918年11月11日に発効した。
The armistice of World War I came into effect on November 11, 1918.
休戦 is the common Japanese word for truce or ceasefire, while アーミスティス is a loanword used mainly in historical or international contexts.
Borrowed from English 'armistice', ultimately from Latin 'arma' (arms) and 'sistere' (to stop).