Иногда я ошибаюсь, когда спешу.

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Breakdown of Иногда я ошибаюсь, когда спешу.

• когда: when
• иногда: sometimes
• спешить: to hurry

Questions & Answers about Иногда я ошибаюсь, когда спешу.

What is the infinitive of ошибаюсь, and what does the -сь ending mean?

The infinitive is ошибаться.

The ending -сь (or -ся) makes the verb reflexive. With ошибаться, it does not mean you literally do something to yourself; instead, it forms a verb whose meaning is simply “to be wrong / to make a mistake.”

So:

• ошибаться = to be mistaken, to make mistakes (imperfective)
• я ошибаюсь = I’m wrong / I make mistakes

There is no non‑reflexive verb ошибать with the same meaning, so you always need the -ся / -сь part with this verb.

Why do we use ошибаюсь (imperfective) here and not the perfective ошибусь?

In Russian, the imperfective aspect is used for:

• repeated / habitual actions
• general truths

The sentence describes a general pattern: “Sometimes I make mistakes when I hurry.” That’s exactly a habitual situation, so imperfective ошибаюсь is natural.

The perfective ошибиться (future: я ошибусь) is for a single, completed mistake:

• Осторожно, не ошибись. – Be careful, don’t make a mistake (this time).
• Я однажды сильно ошибся. – I made a big mistake once.

Using я ошибусь in this sentence would sound like you are predicting a specific future mistake, not talking about a general tendency.