Marie est neuvième.

Est is the third-person singular form of the verb être, which means to be.

So:

• Marie = the subject
• est = is
• neuvième = ninth

That is why Marie est neuvième means Marie is ninth.

Neuvième is an ordinal number, meaning a word like first, second, third, ninth.

In French:

• neuf = nine (cardinal number)
• neuvième = ninth (ordinal number)

So neuvième tells you Marie’s position in an order or ranking, not the quantity.

Because neuvième is being used after the verb être as a predicate adjective.

In English, we also say:

• Marie is ninth not necessarily
• Marie is the ninth

French works similarly here:

• Marie est neuvième = Marie is ninth

If you say Marie est la neuvième, that usually means Marie is the ninth one or gives a more specific sense of identification within a group.

Because neuvième has the same form in the masculine and feminine.

Many French adjectives change visibly:

• petit → petite

But some do not change in spelling between masculine and feminine, and neuvième is one of them.

So:

• un garçon est neuvième
• Marie est neuvième

Both use neuvième.

Yes. In Marie est neuvième, neuvième is functioning like an adjective after être.

It describes Marie’s position, just as an adjective might describe a quality:

• Marie est heureuse = Marie is happy
• Marie est neuvième = Marie is ninth

So although it comes from a number, it behaves grammatically like an adjective here.

Yes, but it is not exactly the same.

• Marie est neuvième = Marie is ninth / in ninth place
• Marie est la neuvième = Marie is the ninth one

The version without the article is very natural when talking about rank or position.

The version with la is more specific and often sounds like you are identifying her as the ninth person/item in a known set.

Because Marie is the subject of the sentence, and you are directly saying something about her.

• Marie est neuvième = You are describing Marie.

C’est is often used for identification, emphasis, or with nouns in different sentence patterns, but here the simple structure is:

• subject + être + adjective
• Marie est neuvième

So Marie est neuvième is the normal choice.

Neuvième is pronounced roughly like nuh-vyem.

A more careful approximation is:

• neu-vième → nuh-vyem

A few points:

• the eu sound does not exist exactly in English
• the vième part sounds a bit like vyem
• the final e is not pronounced as a full extra syllable

Also, in est neuvième, there is no liaison, because neuvième begins with a consonant sound.

They are different kinds of numbers:

• neuf = nine
• neuvième = ninth

Compare:

• Marie a neuf livres. = Marie has nine books.
• Marie est neuvième. = Marie is ninth.

So neuf tells you how many, while neuvième tells you what position.

Yes. Ordinal numbers in French can be used for many kinds of order or rank, such as:

• place in a competition
• order in a list
• school grade or level in some contexts
• floor numbers, chapters, centuries, etc.

So Marie est neuvième simply means Marie is in the ninth position in whatever sequence the context gives you.