I understand that polite forms like yomimasu are actually (or originated as) infinitive yomi + auxiliary verb masu in its plain non-past form. Then past form yomimashita is just infinitive yomi + plain past mashita.

So I wonder what is the origin of the negative form, such as yomimasen. Given the above, one might naively expect a plain non-past negative form of masu, which would give yomimasanai. Is -masen "explainable" in terms of other forms? Is it a contraction from an originally longer form?

2 Answers 2


According to Shogakukan's big 国{こく}語{ご}大{だい}辞{じ}典{てん}, the verb ending -masu ultimately derived from a combination of humble polite auxiliary verb 参{まい}る plus the verb する, as a shift from either ‑mairasuru or possibly ‑maisuru. The final ‑su in modern ‑masu conjugates identically to classical su / suru. The 未然形{みぜんけい} ("incomplete form") that is used to form negatives ends in ‑a in most classical 四段{よだん} verbs (which became modern 五段{ごだん} or "type 1" verbs), such as kaka‑ as the mizenkei for 書{か}く, or ika‑ as the mizenkei for 行{い}く, etc. However, classical su / suru is irregular, and its mizenkei is se‑ instead. (This is still the mizenkei for suru in some modern dialects, such as Kansai-ben.) So the negative of ‑masu was formed as the mizenkei of ‑mase‑ plus the negative ending -nu, as ‑masenu. Final ‑nu contracts to just ‑n, giving us modern ‑masen.


Just wanted to add a little extra context to ます and it's modern day 否定形, ません. ます appears in the Nara period as an honorific way to say be/go. It was later used as a honorary supplementary verb (a verb attached to the end of another verb to show respect/honor). The latter usage survives into the modern day with the same usage.

The difference between classical and the modern day is that the classical verb was a 四段 verb so the 未然形 was まさ and the simple negative was まさず. Eventually the 連体形 of ず (simple negative auxiliary) as well as all verbs/adjectives/adjectival verbs replaced the 終止形 (modern day 辞書形). So まさず become まさぬ. Eventually ぬ (negative auxiliary 連体形/終止形) became ん in 関西 (Kansai region) and ない in 関東 (Tokyo and surrounding areas).

So you would expect like all 五段 verbs that ます would've been conjugated in modern Japanese like まさない or まさん but this clearly isn't the case. Instead it is conjugated like a サ変 verb + ん(ぬー>ん), ません. This is more than likely due to the misinterpretation of ます as being the combination of (何々 "something")+す. This is completely understandable as a lot of verbs in classical/modern Japanese are formed by something + す. For example, to make a Sino-Japanese noun a verb just attach す (or in modern Japanese する). All of the verbs formed this way follow a サ変 conjugation because they are inflections of す/する.

In short. ます exists as a verb with the same function in both classical and modern Japanese. At some point, ます was misinterpreted as a サ変 verb and is now conjugated like a サ変 verb plus ん.

  • Per the argument in the other answer, treating ます as a combination of ま + す isn't actually a misinterpretation. Commented May 12, 2023 at 7:08
  • While the source from above is from a dictionary (published in 1972 originally), it really does seem like a folk etymology as it doesn't really agree with the historical written record from around 1200 years ago.
    – LordVysh
    Commented Sep 22, 2023 at 22:11

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