In Japanese history, a is a warrior specially trained in a variety of unorthodox arts of war. These include assassination, illusion, espionage, and various martial arts.

The exact origin of the ninja is a matter of debate. It is known that ninja appeared in 14th century Japan and remained active from the Kamakura to the Edo period.Fact: date=January 2009 The role of the ninja may have included sabotage, espionage, scouting and assassination as a method of destabilization or to cause social chaos. Such actions may have taken place at the service of a feudal lord (daimyo, shogun), or other entity waging guerilla warfare.Fact: date=February 2009

Etymology

Ninja is the on'yomi reading of the two kanji 忍者 used to write shinobi-no-mono (忍の者), which is the native Japanese word for people who practice ninjutsu (忍術, often erroneously transliterated as ninjitsu). The term shinobi (historically sino₂bi₂ written with the Man'yōgana 志能備), has been traced as far back as the late 8th century to a poemTakagi, Man'yōshū poem #3940; page 191Satake, Man'yōshū poem #3940; page 108 to Ōtomo no Yakamochi. The underlying connotation of shinobi (忍) means "to steal away" and—by extension—"to forbear", hence its association with stealth and invisibility. Mono (者, likewise pronounced sha or ja) means a "person."

The word ninja became popular in the post-World War II culture. The nin of ninjutsu is the same as that in ninja, whereas jutsu (術) means skill or art, so ninjutsu means "the skill of going unperceived" or "the art of stealth"; hence, ninja and shinobi-no-mono (as well as shinobi) may be translated as "one skilled in the art of stealth." Similarly, the pre-war word ninjutsu-zukai means "one who uses the art of remaining unperceived."

Other terms which may be used include oniwaban (お庭番 "garden keeper or gardener"), suppa (素っ破 "thief"), rappa (乱破 "ruffian"), mitsumono, kusa (草 grass) and Iga-mono ("one from Iga").

In English, the plural of ninja can be either unchanged as ninja, reflecting the Japanese language's lack of grammatical number, or the regular English plural ninjas.

Period of origin

Ninja as a group first began to be written about in 14th century feudal Japan as martial organizations predominately in the regions of Iga and Koga of central Japan, though the practice of guerrilla warfare and undercover espionage operations goes back much further.Fact: date=November 2007