Questions & Answers about Я ошибся в одном бланке и попросил у женщины на почте другой.
Ошибся is the past tense, masculine singular form of ошибиться, which means to make a mistake or to be mistaken.
In this sentence, Я ошибся в одном бланке means something like:
- I made a mistake on one form
- literally: I was mistaken in one form
A few useful points:
- я ошибся = I made a mistake (spoken by a man)
- if the speaker were a woman, it would be я ошиблась
- the verb is reflexive because of -ся
So ошибиться is a very common Russian way to say that you got something wrong.
Because the verb ошибиться often uses the pattern:
- ошибиться в чём-то = to make a mistake in something
So:
- в бланке = in the form
- в одном бланке = in one form
After в in this meaning, Russian uses the prepositional case, so:
- бланк → в бланке
- один → в одном
That is why both words change form.