Cumplimos la promesa.

It comes from the verb cumplir.

In this sentence, cumplir means to fulfill, to keep, or to carry out. With la promesa, the natural meaning is to keep/fulfill the promise.

A very useful collocation is:

• cumplir una promesa = to keep/fulfill a promise

So even if English often says keep a promise, Spanish normally uses cumplir here, not a verb that literally matches keep.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

• cumplimos = we fulfill / we fulfilled

So nosotros cumplimos la promesa is possible, but cumplimos la promesa is more natural unless you want emphasis or contrast.

For example:

• Nosotros cumplimos la promesa, pero ellos no.
  = We kept the promise, but they didn’t.

It can mean either one.

For regular -ir verbs, the nosotros form is the same in:

• present indicative: cumplimos = we fulfill / we keep
• preterite: cumplimos = we fulfilled / we kept

So context tells you which one is meant.

Examples:

• Siempre cumplimos la promesa.
  = We always keep the promise. → present

• Ayer cumplimos la promesa.
  = Yesterday we fulfilled the promise. → preterite

Because both forms are spelled the same.

With many regular -ir verbs, the nosotros form in the present and the preterite is identical:

• vivimos
• abrimos
• cumplimos

Spanish does not add an accent mark just to distinguish those two meanings. You understand it from context.

Spanish often uses the definite article when talking about a specific thing already known in the conversation or situation.

So la promesa means the promise.

If you said cumplimos una promesa, that would mean we fulfilled a promise — any promise, not a specific one.

Compare:

• Cumplimos la promesa. = We kept the promise.
• Cumplimos una promesa. = We kept a promise.

Because prometer and cumplir do different things.

• prometer = to promise
• cumplir = to fulfill / keep

So:

• Prometemos algo. = We promise something.
• Cumplimos la promesa. = We keep/fulfill the promise.

A learner can easily confuse these because English uses promise as both a noun and a verb, but Spanish separates the ideas more clearly here.

Yes, but Cumplimos la promesa is the most neutral order.

Other orders are possible for emphasis:

• La promesa la cumplimos.
  This emphasizes the promise.

• Nosotros cumplimos la promesa.
  This emphasizes we.

Spanish word order is more flexible than English, but the basic order here is:

• verb + object

Yes. That is also correct, but it gives a slightly different feel.

• Cumplimos la promesa can be simple past or present, depending on context.
• Hemos cumplido la promesa is the present perfect: we have fulfilled the promise.

In Spain, the present perfect is especially common for recent past actions connected to the present.

So in Spain Spanish, you might often hear:

• Hemos cumplido la promesa.

But Cumplimos la promesa is still perfectly correct.

No. Cumplir is a very common verb with several uses.

Some common ones are:

• cumplir una promesa = to keep a promise
• cumplir una obligación = to fulfill an obligation
• cumplir una norma = to comply with a rule
• cumplir años = to turn years old / have a birthday
• cumplir con algo = to comply with / meet / do what is required

So the core idea is often to fulfill, to meet, or to carry out.

Because la promesa is a thing, not a person.

The personal a is used before specific human direct objects, and sometimes pets or personified beings. But here the direct object is la promesa, which is an inanimate noun.

So:

• Cumplimos la promesa. ✅
• Vemos a María. ✅

No a is needed with la promesa.

A simple pronunciation guide is:

• cumplimos → koom-PLEE-mos
• la → lah
• promesa → proh-MEH-sah

In IPA (roughly, in standard Spain Spanish):

• [kumˈplimos la pɾoˈmesa]

A few tips:

• u in cumplimos sounds like the oo in food, but shorter.
• The stress is on -pli-: cum-PLI-mos
• The r in promesa is a light Spanish tap.
• The s sound is clear and crisp.

It is neutral. It can work in both formal and informal contexts.

• In everyday speech: Cumplimos la promesa.
• In writing or formal speech: also perfectly fine

What makes it formal or informal is usually the wider context, not this sentence by itself.

You can add emphasis in a few ways:

• Sí, cumplimos la promesa.
  = Yes, we did keep the promise.

• Nosotros cumplimos la promesa.
  = We kept the promise. (emphasizing we)

• La promesa sí la cumplimos.
  = We did keep the promise. (emphasizing the promise)

These are all natural, but the plain sentence Cumplimos la promesa is the most neutral version.