In Japanese the mashita ending is the past form of polite verbs.

For example:

To buy (root form) - Kau
To buy (polite form) - kaimasu 
To buy (polite form, past) - kaimashita

In my Japanese text book it has the following example

Where did you buy it?
Doko de kattan desu ka?

Why is the speaker using kattan instead of kaimashita (especially as kattan is defined as coal)? Could kattan be substituted with kaimashita? How does the meaning change when using kattan or kaimashita?

  • 1
    katta is the informal past tense of kau. For the 'n' part try looking up the phrase 'explanatory の' and see this question japanese.stackexchange.com/questions/506/… Feb 28, 2017 at 16:52
  • And this: japanese.stackexchange.com/q/5398/5010 If you're okay, I think this can be closed as a duplicate of either of these questions.
    – naruto
    Feb 28, 2017 at 17:03
  • @naruto So is the speaker using kattan (instead of Kaimashita) to be more informal and to soften the question so it's not so demanding. And so, yes, you can switch it with Kaimashita?. But then does that mean it is always better to use n desu forms to avoid sounding rude when asking questions? Is that correct? Also, is to buy another meaning of Kattan? (In addition to coal?) Thanks!
    – big_smile
    Feb 28, 2017 at 18:18
  • 1
    You're misunderstanding the parse. nda/ndesu is a contraction of noda/nodesu, which @user3856370 linked above.
    – Kurausukun
    Feb 28, 2017 at 20:03
  • 1
    @big_smile (1) Kattan is not a conjugation form. It's katta (ta-form) + no (contracted to n) + desu + ka. (2) Neither is milder nor politer than the other. no/n has an important role and omitting it would sound very awkward. Please read the linked answers carefully.
    – naruto
    Mar 1, 2017 at 3:07

1 Answer 1


To buy (root form) - Kau
To buy (polite form) - kaimasu, (casual form) - kau
To buy (polite form, past) - kaimashita, (casual form, past) - katta

Where did you buy it?
Doko de kattan desu ka? = Doko de katta no desu ka?

"Katta" is a casual and past form, but "katta no desu ka?" is a polit form because it has "desu."

"Kattan desu (ka?)" is a short form of "Katta no desu (ka?)"

Doko de kattan desu ka? = Doko de kai mashita ka?

Both are polite. The latter is more polite. The former is a spoken vocabulary.

  • Dear the person who gamve me negative evaluation, I'd like to know why. Or I can't improve my answer. Mar 1, 2017 at 11:36
  • I didn't downvote you. I think your answer is helpful. The former is a spoken vocabulary. Does that mean the latter (kai mashita) wouldn't sound as natural as when spoken (e.g. the former is better to use when speaking). Is that correct? Thanks!
    – big_smile
    Mar 1, 2017 at 18:17

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