Я клянусь говорить правду.

I swear to tell the truth.

Breakdown of Я клянусь говорить правду.

• я: I
• правда: the truth
• говорить: to tell / to say
• клясться: to swear; vow

Questions & Answers about Я клянусь говорить правду.

What form is клянусь?

Клянусь is the 1st person singular form of клясться, which means to swear.

So:

• клясться = to swear
• я клянусь = I swear

This verb is a little irregular, so the form does not look exactly like the infinitive. A few present-tense forms are:

• я клянусь
• ты клянёшься
• он / она клянётся
• мы клянёмся

So in this sentence, клянусь is simply the verb form that matches я.

Why does клянусь end in -сь?

Because the dictionary form of the verb is клясться, a reflexive verb.

In Russian, reflexive verbs end in:

• -ся
• or -сь

After a vowel, Russian usually uses -сь, so:

• клянусь
• not клянусся

Here, the reflexive ending is just part of the verb. It does not mean the sentence is literally reflexive in the English sense, like I wash myself. Many Russian verbs are simply used in a reflexive form as part of their normal meaning.

So you should learn клясться as a whole verb meaning to swear.