Learn Hardcore French: Je leur écris un message pour confirmer le dîner. - I write them a message to confirm dinner.

Ils = subject pronoun: Ils viennent. (They are coming.)
Eux = stressed/disjunctive pronoun, used after prepositions or for emphasis: Je parle avec eux. (I’m talking with them.)
Leur (here) = indirect object pronoun, meaning to them, used before the verb: Je leur écris. (I am writing to them.)

In Je leur écris un message, leur replaces à eux (to them), so leur is the correct choice, not ils or eux.

What exactly does leur mean here, and why is there no à in the sentence?

The verb écrire is often used with à:

écrire à quelqu’un = to write to someone
J’écris à mes parents. → Je leur écris.

When you replace à mes parents with a pronoun, à disappears and is absorbed into the indirect object pronoun leur, which must go before the verb:

Je écris à eux ❌
Je leur écris ✅

So leur already includes the idea of to them; that’s why there is no separate à.

Why is it Je leur écris un message and not Je écris leur un message?

In French, unstressed object pronouns (like me, te, lui, nous, vous, leur, le, la, les) go before the conjugated verb, in a fixed order.

Basic pattern:
subject + (object pronoun) + verb

So:

Je leur écris un message ✅
Je écris leur un message ❌ (wrong position)

English word order doesn’t work here; you must put leur before écris.

Does Je leur écris un message mean “I write them a message” or “I am writing them a message”?

It can mean both.

French has only one simple present tense:

Je leur écris un message can be:
- I write them a message (habitual)
- I am writing them a message (right now / around now)

Context usually tells you whether it’s a general habit or something happening now.

Can I say Je leur écris pour confirmer le dîner and skip un message?

Yes, absolutely.

Je leur écris un message pour confirmer le dîner.
Focuses on the medium: you are sending a message (not calling, not visiting, etc.).
Je leur écris pour confirmer le dîner.
More general: you are writing to them (email, text, etc.) to confirm.

Both are correct; the second is often more natural in conversation because you don’t always need to mention un message explicitly.

Why is confirmer in the infinitive after pour?

Pour + infinitive is a common structure meaning in order to + verb.

Je leur écris un message pour confirmer le dîner.
= I am writing them a message (in order) to confirm the dinner.

Other examples:

Je prends le bus pour aller au travail. (…to go to work)
Il étudie pour réussir l’examen. (…to pass the exam)

So pour confirmer is the normal way to express to confirm as a purpose.

Why is it le dîner and not un dîner or just dîner without an article?

Here dîner is a noun, meaning the dinner (a specific dinner that both speaker and listener know about, e.g. a planned dinner).

le dîner = the specific dinner we’re referring to
un dîner = a dinner (non-specific, one of many)
dîner without an article is usually the verb:
- Nous allons dîner. (We are going to have dinner.)

In pour confirmer le dîner, the definite article le shows that it is a particular, already-arranged event.

Is dîner here a noun or a verb, and what’s the difference?

In this sentence, dîner is a noun:

le dîner = the dinner (meal/event)

As a verb, dîner means to have dinner / to dine:

Nous dînons à 20 h. (We have dinner at 8 p.m.)
On va dîner chez Paul. (We’re going to have dinner at Paul’s place.)

So:

Je leur écris un message pour confirmer le dîner.
→ dîner = noun (with article le)
Je leur écris pour dîner avec eux.
→ dîner = verb (infinitive, no article)

How would the sentence change if I were writing to just one person (him or her) instead of several people?

You would replace leur (to them) with lui (to him / to her):

Je lui écris un message pour confirmer le dîner.
= I’m writing him/her a message to confirm the dinner.

Lui is the singular indirect object pronoun corresponding to à lui / à elle.

How could I say “I’m writing it to them” using only pronouns?

First, identify the two objects:

un message → le (direct object pronoun, masculine singular)
à eux → leur (indirect object pronoun)

The order of object pronouns before a single conjugated verb is:

me, te, se, nous, vous
le, la, les
lui, leur

So:

Je le leur écris.
= I’m writing it to them.

This replaces Je leur écris un message when the context already makes un message clear.

Can I use other words instead of un message, like “a text” or “an email”?

Yes. Common alternatives include:

un texto / un SMS = a text message
un mail / un e-mail (very common in everyday French)
un courriel (more formal / used especially in Canada)
une lettre = a letter

Examples:

Je leur écris un texto pour confirmer le dîner.
Je leur envoie un mail pour confirmer le dîner. (note écrire → envoyer fits better with mail in many contexts)

Can I use pour to mean “to someone” in this sentence, like J’écris un message pour eux?

Be careful here; pour and à don’t work the same way with écrire:

écrire à quelqu’un = write to someone (recipient)
- J’écris un message à mes amis.
- Je leur écris un message.
écrire un message pour quelqu’un usually means you write a message for someone’s benefit / on their behalf, not that they are the recipient.
- J’écris un message pour mon collègue.
  → I’m writing a message for my colleague (maybe instead of him, or to help him).

In Je leur écris un message, leur clearly marks them as the recipients. If you say J’écris un message pour eux, it can sound like you’re doing it for them, but not necessarily to them. Context is needed, and the nuance is different.