Ce couteau sert à couper le pain.

Ce is a demonstrative adjective. It can mean either this or that, depending on the context.

So ce couteau can mean:

• this knife
• that knife

French does not always make the same clear distinction between this and that that English does. If the speaker wants to be more specific, they can say:

• ce couteau-ci = this knife
• ce couteau-là = that knife

French uses:

• ce before a masculine singular noun that starts with a consonant sound
• cet before a masculine singular noun that starts with a vowel sound or silent h

Since couteau starts with the consonant sound k, you say ce couteau.

Compare:

• ce livre
• ce couteau
• cet homme
• cet arbre

Sert is the third-person singular present of the verb servir.

The subject is ce couteau, which is singular, so the verb must also be singular:

• je sers
• tu sers
• il/elle/on sert

So ce couteau sert... means this/that knife serves... or more naturally this knife is used...

Servir à means to be used for or to serve to.

So:

• Ce couteau sert à couper le pain = This knife is used for cutting bread / This knife is for cutting bread

It is a very common French structure:

• Cette clé sert à ouvrir la porte = This key is used to open the door
• Une cuillère sert à manger la soupe = A spoon is used to eat soup

Because the verb servir often takes the pattern servir à + infinitive when you say what something is used for.

So the structure is:

subject + servir + à + infinitive

Examples:

• Ce stylo sert à écrire
• Cette machine sert à laver
• Ce couteau sert à couper

You just have to learn servir à as a set pattern.

After à in this structure, French uses the infinitive.

So:

• sert à couper not
• sert à coupe not
• sert à coupe le pain

This is similar to English used to cut or for cutting.

Other examples:

• Il apprend à conduire = He is learning to drive
• Une brosse sert à nettoyer = A brush is used to clean

French often uses the definite article where English might use no article or a different one.

Here, le pain can refer to bread in a general sense: bread as the thing being cut.

So couper le pain is a natural French expression for cut bread or cut the bread, depending on context.

Compare:

• manger du pain = to eat some bread
• couper le pain = to cut the bread / cut bread

With action verbs like couper, French often uses le/la/les more than English learners expect.

Yes, you might hear that, and it would be understood, but sert à is usually the more natural and standard way to say that something is used for a purpose.

So:

• Ce couteau sert à couper le pain = very natural
• Ce couteau est pour couper le pain = understandable, but less idiomatic in many contexts

A very common alternative is:

• C’est un couteau à pain = It’s a bread knife

That version names the object rather than describing its function.

Not exactly.

• servir à + infinitive describes the function or use of something
• pour + infinitive often expresses purpose, but not always in the same way

For objects, servir à is often the best choice:

• Cette boîte sert à ranger des photos = This box is used to store photos

You can sometimes use pour, but servir à sounds especially natural when talking about what an object is designed or meant to do.

Couteau is pronounced approximately koo-toh.

A few useful points:

• the cou sounds like koo
• the ending -teau sounds like toh
• the final x in the plural couteaux is silent

So:

• un couteau
• des couteaux

The singular and plural sound almost the same in isolation.

Yes: the final t in sert is normally silent here.

So sert à is pronounced roughly like ser ah, not sertah.

There is no pronounced t between sert and à in normal speech.

That makes the whole sentence flow roughly like: Ce couteau ser ah koo-pay luh pan

Yes. On its own, ce couteau can mean either this knife or that knife. Context tells you which one is meant.

If you want to force the distinction, French can add:

• ce couteau-ci = this knife
• ce couteau-là = that knife

But in everyday speech, people often just say ce couteau and let the situation make it clear.

Yes.

• Ce couteau sert à couper le pain = This/that knife is used to cut bread
• Un couteau sert à couper le pain = A knife is used to cut bread

So ce points to a particular knife, while un makes it more general.

The second sentence sounds more like a general statement about what a knife is for.