Marie voit le mouton.

Because Marie is a proper noun: a person’s name. In French, you normally do not put an article before someone’s name in a basic sentence.

So:

• Marie voit le mouton. = Marie sees the sheep.

Not:

• La Marie voit le mouton. in standard basic French

In some regional or informal speech, you may sometimes hear articles before names, but that is not the normal pattern learners should use first.

Voit is the third-person singular form of the verb voir, which means to see.

Here is the present tense of voir:

• je vois = I see
• tu vois = you see
• il / elle / on voit = he / she / one sees
• nous voyons = we see
• vous voyez = you see
• ils / elles voient = they see

Since Marie is she, French uses voit.

In French, nouns usually need a determiner before them, such as:

• le / la / les = the
• un / une / des = a, an, some
• ce / cette / ces = this, that, these, those
• mon / ma / mes = my

So French usually says:

• le mouton
• un mouton

not simply:

• mouton

English can sometimes omit an article more easily than French, but French generally cannot.

Yes. Mouton is a masculine singular noun, so it takes le in the definite form:

• le mouton = the sheep
• un mouton = a sheep

French nouns have grammatical gender, and the article must match the noun:

• masculine singular: le
• feminine singular: la
• plural: les

The gender is grammatical, so it does not mean the sheep is biologically male. It is just the grammatical gender of the noun mouton.

A simple pronunciation guide is:

• Marie ≈ ma-REE
• voit ≈ vwah
• le ≈ luh (with a French eu sound)
• mouton ≈ moo-TOHN with a nasal ending

A rough IPA version is:

• Marie voit le mouton → /ma.ʁi vwa lə mu.tɔ̃/

A few important points:

• The r in French is not the English r.
• The t in voit is usually silent.
• The final n in mouton is not pronounced like an English n. It helps create a nasal vowel: -ton here sounds more like tɔ̃.

Normally, no important liaison is made here in careful standard pronunciation.

• Marie voit: no liaison
• voit le: no liaison, because the final t in voit does not link here
• le mouton: no liaison, because le does not normally make one before mouton

So the words stay fairly separate:

• Marie / voit / le / mouton

That is helpful for beginners, because this sentence is pronounced quite close to the written word groups.

Because this is a simple subject + verb + object sentence.

• Marie = subject
• voit = verb
• le mouton = direct object

So:

• Marie voit le mouton. literally follows:
• Marie sees the sheep.

French and English often use the same basic order in simple statements, though French differs more in questions, object pronouns, negation, and some other structures.

Yes. That changes the meaning slightly:

• Marie voit le mouton. = Marie sees the sheep
• Marie voit un mouton. = Marie sees a sheep

So the difference is the same basic one as in English:

• le = the
• un = a / an

Use le when the sheep is specific or already known in context. Use un when it is not specific or is being introduced for the first time.

In a way, it does change. French verbs are conjugated, but the endings are different from English.

The infinitive is voir.
With Marie, you use voit.

So French marks the third-person singular with the form voit, just as English marks it with sees.

Compare:

• English: I see, she sees
• French: je vois, Marie voit

So the verb is changing; it is just changing according to French rules.

Yes, depending on context, mouton can refer to:

• a sheep (the animal)
• mutton (the meat)

But in a simple sentence like Marie voit le mouton, the natural meaning is the sheep, the animal.

If the context were about food, then mouton could be understood differently. Context usually makes it clear.

You would change the subject and conjugate voir to match it:

• Je vois le mouton. = I see the sheep.
• Nous voyons le mouton. = We see the sheep.

So the object le mouton stays the same, but the verb changes:

• Marie voit
• je vois
• nous voyons

This is one of the main things French learners need to watch: the verb must agree with the subject.

Yes, in several ways:

• Marie voit le mouton ?
  Informal spoken question, using rising intonation.

• Est-ce que Marie voit le mouton ?
  Very common and natural way to ask it.

• Marie voit-elle le mouton ?
  More formal inversion style.

All three mean:

• Does Marie see the sheep?

For a beginner, Est-ce que Marie voit le mouton ? is often the easiest question form to learn first.

You would get:

• Elle voit le mouton. = She sees the sheep.

This is useful because it shows that Marie behaves grammatically like elle:

• Marie voit
• elle voit

That is why the verb form is voit in both cases. French chooses the verb form based on the grammatical person and number of the subject.