La septième personne arrive.

Because personne is a feminine noun in French. French articles have to agree with the gender of the noun, so you say la personne, not le personne.

Even though the person could be male or female in real life, the noun personne is always grammatically feminine.

Sept means seven.

Septième means seventh.

So:

• sept personnes = seven people
• la septième personne = the seventh person

This is the difference between a cardinal number and an ordinal number:

• cardinal: one, two, three
• ordinal: first, second, third

In French, ordinal numbers usually come before the noun, just like in English.

So:

• la première personne
• la deuxième personne
• la septième personne

This matches English structure:

• the first person
• the second person
• the seventh person

Some French adjectives change visibly between masculine and feminine, but septième has the same written form for both masculine and feminine singular.

So you get:

• le septième jour
• la septième personne

The article changes from le to la, but septième stays the same.

Arrive is the present tense of the verb arriver.

Here it is the third-person singular form, used with la septième personne.

So:

• j’arrive = I arrive / I am arriving
• tu arrives = you arrive
• il / elle arrive = he / she arrives
• la personne arrive = the person arrives

It can mean either one, depending on context.

French present tense often covers both:

• simple present: arrives
• present progressive: is arriving

So La septième personne arrive could mean:

• The seventh person arrives
• The seventh person is arriving

Usually the context tells you which sounds more natural in English.

Because French does not always use a separate verb like English does in is arriving.

In this sentence, the single verb arrive already expresses the present action.

French can use a longer form such as est en train d’arriver to stress that something is happening right now, but that is not necessary here.

So:

• La septième personne arrive = normal, natural French
• La septième personne est en train d’arriver = the seventh person is in the process of arriving

Because here arrive is a verb, not an adjective or past participle.

In La septième personne arrive:

• arrive = present-tense verb

By contrast:

• arrivée can be a past participle or a noun related to arrival, depending on context

For example:

• La personne est arrivée. = The person has arrived.
• l’arrivée = the arrival

So in your sentence, arrive is correct because the sentence needs a present-tense verb.

A helpful approximation is set-yem.

A few things to notice:

• the p in septième is usually not pronounced
• the ending -ième sounds roughly like yem
• the stress in French is much flatter than in English

So septième is commonly pronounced close to set-yem.

A simple approximation is:

la set-yem pair-sonn ah-reev

More carefully:

• La = la
• septième = set-yem
• personne = pair-sonn
• arrive = ah-reev

Also, in natural speech, French flows smoothly, so the words connect more than in English.

Yes, personne can mean two different things in French:

1. a person

   • une personne
   • la septième personne

2. nobody / no one, usually in a negative structure

   • Personne ne vient. = Nobody is coming.

In your sentence, personne is clearly the noun meaning person, because it has the article la and is modified by septième.

Because the sentence is talking about one specific person: the seventh one.

So:

• la septième personne = one person
• les sept personnes = seven people

An ordinal like seventh identifies position in a sequence, so it usually refers to one item.

Yes.

Even though personne is grammatically feminine, it can refer to any human being, regardless of biological sex.

So la septième personne could be:

• the seventh woman
• the seventh man
• the seventh person of unspecified gender

The feminine article is there because of the noun personne, not because the actual person must be female.

Yes, especially in less formal writing.

You may see:

• La 7e personne arrive.

That means the same thing as:

• La septième personne arrive.

The fully written form septième is often preferred in standard sentences for learners, formal writing, or when clarity matters.

Yes. If you mean a seventh person rather than the seventh person, you would use une instead of la:

• Une septième personne arrive. = A seventh person is arriving.

So:

• la septième personne = the seventh person, a specific one in an order
• une septième personne = a seventh person, introducing another person into the situation