Translation guide
The iconic sword associated with ninja, often shorter and straighter than a katana, used for stealth and utility.
Referring to the standard sword used by ninja in popular culture and history
The most common and direct term for a ninja sword. It refers to the straight-bladed, shorter sword often depicted in media.
忍者刀は普通の刀より短くてまっすぐです。
A ninja sword is shorter and straighter than a regular katana.
An alternative term, literally 'stealth sword'. Slightly more traditional or literary feel.
忍刀は忍者が使っていたとされる刀です。
The shinobigatana is a sword said to have been used by ninja.
Discussing the actual historical weapon, which may differ from pop culture depictions
Even in historical discussions, 忍者刀 is the standard term, though historians may note that its exact form is debated.
歴史的な忍者刀の形状については諸説あります。
There are various theories about the shape of historical ninja swords.
Referring to the weapon in movies, anime, games, etc.
The go-to term in any modern context.
そのアニメの主人公は忍者刀を背負っています。
The main character of that anime carries a ninja sword on his back.
While often called a 'ninja sword' in English, it is distinct from a katana. In Japanese, 刀 (かたな) is a broad term, but 忍者刀 specifically implies the ninja version. Avoid calling it 忍者刀 when you mean a regular katana.