Etymology 1Edit

From Old Japanese. The adjectivizing suffix appears to derive ultimately from ancient copula or stative verb ‎(nu).


ない ‎(romaji -nai)

  1. used to form derivative -i adjectives from other terms: having that quality, having that state; very much that quality or state
     (せつ)ない (いと)ない、ぎこちない
    setsunai, itokenai, gikochinai
    very moving, really young of manner, having clumsiness
Derived termsEdit

Etymology 2Edit

From the attributive form of the Early Middle Japanese adjective nashi: /naki/ > /nai/, with the medial /-k-/ falling out.


ない ‎(-i inflection, romaji nai)

  1. not, there is no, lack
    スプーンが ()
    Supūn ga nai.
    There is no spoon.
Usage notesEdit

In public speech and written language, irregular expressions ありません ‎(arimasen) and ありませんでした ‎(arimasendeshita) (past) are recommended instead of ないです and なかったです.

Alternative formsEdit

Etymology 3Edit

First appears in texts from the late Muromachi period as an eastern-dialect term. Sometimes described as related to ancient eastern-dialect negative ending なふ ‎(nafu), but there is a sizable gap of time between the apparent disappearance of nafu and the emergence of nai.[1]

That said, both nafu and nai probably derive ultimately from ancient copula or stative verb ‎(nu), with the negative sense originating from the 未然形 ‎(mizenkei, irrealis or incomplete form) of the verb stem, to which these endings attach.

The nai ending conjugates as a regular -i adjective just like the adjective nai in modern Japanese, but the ending conjugation is originally different from the adjective. In the Edo period, the ending conjugated irregularly, including nanda instead of modern nakatta (past), and naikereba instead of modern nakereba (conditional).[1]


ない ‎(romaji -nai)

  1. (auxiliary) not, don't
    学校 (がっこう) ()ない
    Gakkō ni ikanai.
    I don't go to school.
Usage notesEdit

Generally, ません ‎(masen) and ませんでした ‎(masendeshita) (past) are recommended for formal negative endings instead of ないです and なかったです.

  • (rare, archaic) ‎(nu)
  • (very casual, also archaic, also dialectal) ‎(n)
  • (Kansai) へん ‎(hen)


  1. 1.0 1.1 1988, 国語大辞典(新装版) (Kokugo Dai Jiten, Revised Edition) (in Japanese), Tōkyō: Shogakukan