In Japanese the mashita ending is the past form of polite verbs.
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?
kattan(instead ofKaimashita) to be more informal and to soften the question so it's not so demanding. And so, yes, you can switch it withKaimashita?. But then does that mean it is always better to usen desuforms to avoid sounding rude when asking questions? Is that correct? Also, is to buy another meaning ofKattan? (In addition to coal?) Thanks! – big_smile Feb 28 '17 at 18:18katta(ta-form) +no(contracted ton) +desu+ka. (2) Neither is milder nor politer than the other.no/nhas an important role and omitting it would sound very awkward. Please read the linked answers carefully. – naruto Mar 01 '17 at 03:07