Mi hermano prometió no mentirnos otra vez.

My brother promised not to lie to us again.

Breakdown of Mi hermano prometió no mentirnos otra vez.

• mi: my
• el hermano: the brother
• prometer: to promise
• nos: us
• no: not
• otra vez: again
• mentir: to lie

Questions & Answers about Mi hermano prometió no mentirnos otra vez.

Why is no placed before mentirnos and not before prometió?

In Spanish, to say “promised not to do something,” the negation goes directly before the infinitive.

• Prometió no mentirnos otra vez = “He promised not to lie to us again.”
  If you put no before prometió (as in Mi hermano no prometió mentirnos otra vez), it means “my brother didn’t promise to lie to us again,” i.e. he made no promise at all.

Why is the pronoun nos attached to the end of mentir?

Spanish allows object pronouns to attach to infinitives. You have two options:

1. Attach to the infinitive:
   
   • Mi hermano prometió no mentirnos otra vez.
2. Place before the conjugated verb:
   
   • Mi hermano nos prometió no mentir otra vez.
     Both are correct, but attaching to the infinitive (mentirnos) is very common.

Why is prometió in the preterite rather than the imperfect?

• The preterite (prometió) describes a completed action or promise made at a specific point in the past.
• The imperfect (prometía) would imply an ongoing or habitual action in the past, which doesn’t fit here since it’s clearly one single promise.

What does mentirnos mean exactly?

Mentir = “to lie”
nos = indirect object pronoun for “us”
So mentirnos literally means “to lie to us.”

Is nos here a direct or indirect object pronoun?

It’s an indirect object pronoun because mentir takes an indirect object (you lie to someone).

Could we use volver a instead of otra vez?

Yes. You can say:

• Mi hermano prometió no volver a mentirnos.
  This structure (volver a + infinitive) also expresses “to do something again.”

What’s the difference between otra vez and de nuevo?

Both mean “again.”

• Otra vez is very common in everyday speech.
• De nuevo is a bit more formal or typical in writing.
  You can usually swap them without changing the meaning.

Could we rephrase it with a subordinate clause and a different tense?

Yes. A common alternative is:

• Mi hermano prometió que no nos mentiría otra vez.
  Here you use a subordinate clause with the conditional (mentiría) to express a future action relative to the past (“future-in-the-past”).