Avui em fa mal el peu.

Because Catalan very often expresses pain with the pattern fer mal a algú = to hurt someone / to cause pain to someone.

So the sentence is built like this:

• Avui = today
• em = to me
• fa mal = hurts / causes pain
• el peu = the foot

Literally, it is something like Today, the foot causes pain to me.

That sounds odd in English, but it is a very normal Catalan structure.

Em is the unstressed pronoun meaning to me.

In this sentence, it shows who feels the pain:

• em fa mal = it hurts me
• et fa mal = it hurts you
• li fa mal = it hurts him/her

So em does not mean my here. It means to me.

Because em is the normal unstressed object form used before most verbs in standard Catalan.

For example:

• em fa mal = it hurts me
• em diu = he/she tells me
• em veu = he/she sees me

You may sometimes see m' before a vowel or silent h:

• m'agrada = I like it
• m'ha dit = he/she has told me

But before fa, the correct form is em.

With body parts, Catalan usually uses the definite article, not the possessive, when the owner is already clear from the pronoun.

So:

• Em fa mal el peu = My foot hurts / My foot is hurting me
• literally: The foot hurts me

Because em already tells us whose foot it is, Catalan normally does not need meu.

This is very common with body parts:

• Em rento les mans = I wash my hands
• Li fa mal el cap = His/Her head hurts
• Ens fan mal les cames = Our legs hurt

Using el meu peu is possible in some contexts, but it is less natural here unless you want special emphasis.

Fa is the he/she/it form of fer in the present tense.

Here, the subject is el peu, which is singular, so the verb must also be singular:

• el peu fa mal = the foot hurts
• els peus fan mal = the feet hurt

So in Avui em fa mal el peu, fa agrees with el peu.

Yes. That would mean Today my feet hurt.

Compare:

• Avui em fa mal el peu = Today my foot hurts / one foot hurts
• Avui em fan mal els peus = Today my feet hurt

The verb changes with the subject:

• el peu fa
• els peus fan

Because the sentence is talking about one foot hurting, not both.

Even if the speaker does not specify left or right, singular el peu is perfectly normal if only one foot is painful.

If you want to be more specific, you can say:

• Em fa mal el peu dret = My right foot hurts
• Em fa mal el peu esquerre = My left foot hurts

Yes. Catalan word order is flexible, though some orders are more neutral than others.

The neutral version here is:

• Avui em fa mal el peu

You could also hear:

• Em fa mal el peu avui
• El peu em fa mal avui

These can change the emphasis slightly:

• Avui first emphasizes today
• El peu first emphasizes the foot

But the original sentence is very natural and standard.

Yes, you can. Doldre is another verb meaning to hurt / to ache.

So:

• Em fa mal el peu
• Em dol el peu

Both are correct.

However, fer mal is extremely common in everyday speech and is often the safer, more widely used pattern for learners.

You can say that too, but it is a slightly different structure.

• Em fa mal el peu = My foot hurts / The foot hurts me
• Tinc mal al peu = I have pain in my foot

Both are natural, but em fa mal el peu is a very common way to talk about pain in Catalan.

Also notice the difference:

• el peu = the foot itself is the subject
• al peu = in the foot / at the foot

So al peu is used with a different construction.

You can simply use intonation in speech:

• Avui et fa mal el peu? = Does your foot hurt today?

Or in writing, the same word order works with a question mark:

• Et fa mal el peu?

Catalan does not need an extra verb like English does.

Put no before the pronoun and verb:

• Avui no em fa mal el peu = Today my foot does not hurt

This is the normal Catalan way to negate the sentence.

Peu is pronounced roughly like peh-oo said quickly as one syllable, though English does not have an exact equivalent.

A simple learner-friendly approximation is:

• peu ≈ peh-ooh compressed into one syllable

Also:

• Avui is roughly ah-VUI
• fa mal is straightforward: fa mal
• el peu links smoothly in speech

If you are learning Central Catalan pronunciation, listening to native audio is especially helpful for eu, since it is not a simple English vowel.

No. It just adds the idea of today.

Without it, you get:

• Em fa mal el peu = My foot hurts

With it:

• Avui em fa mal el peu = Today my foot hurts

So avui gives a time frame, but the basic grammar of the sentence stays the same.