Quand j’ai mal à la mâchoire, je mâche plus lentement et je parle moins.

Quand means when. At the start of a sentence like this, it introduces a time clause:

Quand j’ai mal à la mâchoire = When my jaw hurts / When I have jaw pain

In everyday French, quand can mean either when or whenever, depending on context. Here it sounds like a general situation: Whenever my jaw hurts, ...

French avoids having two vowel sounds next to each other when possible. So je becomes j’ before a word starting with a vowel or silent h.

• je ai → j’ai
• je aime → j’aime

This is called elision.

French often uses the structure avoir mal à + body part to say that something hurts.

So:

• j’ai mal à la tête = I have a headache / my head hurts
• j’ai mal au dos = my back hurts
• j’ai mal à la mâchoire = my jaw hurts

This is more natural in French than trying to translate English word for word.

With body parts, French often uses the definite article (le, la, les) instead of a possessive like my.

So French prefers:

• j’ai mal à la mâchoire
• literally: I have pain at the jaw

Even though English says my jaw, French usually uses the jaw because it is already obvious whose body part it is.

It depends on the gender and number of the noun after à.

• à + le = au
• à + la = à la
• à + l’ = à l’
• à + les = aux

Examples:

• j’ai mal au bras = my arm hurts
• j’ai mal à la jambe = my leg hurts
• j’ai mal à l’épaule = my shoulder hurts
• j’ai mal aux dents = my teeth hurt

Since mâchoire is feminine singular, you get à la mâchoire.

They are related words.

• mâcher = to chew
• je mâche = I chew / I am chewing
• la mâchoire = the jaw

So the sentence uses both the body part and the action connected with it:

• mâchoire = jaw
• mâche = chew

This is a nice example of related vocabulary.

Both verbs are in the present tense:

• je mâche = I chew / I am chewing
• je parle = I speak / I am speaking

In this sentence, the present tense expresses a habitual or general truth:

When my jaw hurts, I chew more slowly and speak less.

It is not just about one specific moment; it describes what usually happens.

Lentement means slowly.
Plus lentement means more slowly.

So:

• je mâche lentement = I chew slowly
• je mâche plus lentement = I chew more slowly

Here, plus is making a comparison, even if the second part of the comparison is only understood: more slowly than usual.

Moins means less. In French, it can stand on its own if the rest is understood.

• je parle moins = I speak less

This usually means less than usual or less than before. French does not need to add another adverb after moins here.

In simple sentences, French adverbs often come after the verb.

• je mâche plus lentement
• je parle moins

This is normal word order in French. English also often does something similar:

• I chew more slowly
• I speak less

So this part is fairly close to English.

French often repeats the subject pronoun in coordinated clauses:

• je mâche plus lentement et je parle moins

This is very natural and clear.
You may sometimes hear or see the subject omitted in very informal or stylistic contexts, but repeating je is the safest and most standard choice.

In plus lentement, plus is pronounced because it means more in a comparison.

So it sounds roughly like plys.

That is different from some negative expressions, where the final s may be silent:

• je ne parle plus = I no longer speak

But in this sentence:

• plus lentement = pronounce the s

They are different accents with different jobs.

• à has a grave accent. It helps distinguish à from a.

  • a = has
  • à = to, at, in

• â in mâche and mâchoire is a circumflex. In modern French, it usually does not change the meaning in a way beginners need to worry much about, but it is part of the correct spelling and can slightly affect pronunciation or reflect the word’s history.

So you should learn these words with their accents:

• à
• mâche
• mâchoire

It most naturally describes a general habit or usual reaction:

Whenever my jaw hurts, I chew more slowly and talk less.

If you wanted to describe one specific occasion, French could still use the present in some contexts, but without extra context this sentence sounds general.

Yes. That is also correct French.

• Quand j’ai mal à la mâchoire = When my jaw hurts
• Quand ma mâchoire me fait mal = When my jaw hurts

The version with avoir mal à is very common and often more idiomatic for beginners to learn first. The faire mal version is also natural, but it is built differently:

• ma mâchoire me fait mal
• literally: my jaw causes pain to me