Learn Hardcore French: Je prends un taxi pour aller au nord de la ville. - I take a taxi to go to the north of the city.

You have already identified which taxi:
- Je prends le taxi qui est devant l’hôtel. – I’m taking the taxi in front of the hotel.
You are speaking in a very general, habitual way:
- Le matin, je prends le taxi pour aller au travail. – In the morning, I take a taxi to go to work.

In your sentence, it is a one-time, unspecified taxi, so un taxi is natural.

Why is the verb prendre used? Why not Je vais en taxi?

In French, prendre is the usual verb for using a means of transport:

prendre le bus – to take the bus
prendre le train – to take the train
prendre un avion – to take a plane
prendre un taxi – to take a taxi

Je prends un taxi focuses on the action of picking/using that transport.

You can also say Je vais en taxi, which is correct and means I go by taxi, focusing more on the way you are travelling than the act of taking it. Both are fine, but prendre is extremely common and often sounds more natural.

Is prendre used with all kinds of transport?

Mostly yes, for vehicles and public transport:

prendre le bus / le métro / le tram / le train / l’avion / un taxi / un Uber
Also: prendre la voiture – to take the car (drive)

You do not use prendre with:

Walking: aller à pied, not prendre à pied
Cycling: usually aller à vélo, but prendre le vélo is possible when you mean “take the bike (instead of something else)”.

So Je prends un taxi fits the normal pattern for transport.

What does pour aller mean here? Is pour just for?

Here pour means in order to, expressing purpose:

Je prends un taxi pour aller au nord de la ville.
→ I’m taking a taxi in order to go to the north of the city.

Structure: pour + infinitive = to / in order to + verb
Examples:

Je viens pour t’aider. – I’m coming to help you.
Il travaille pour gagner de l’argent. – He works to earn money.

So pour aller is “to go / in order to go”, not “for going” in the English sense.

Can I say Je prends un taxi aller au nord de la ville without pour?

No. That is incorrect in French.

You must keep pour before the infinitive:

✅ Je prends un taxi pour aller au nord de la ville.
❌ Je prends un taxi aller au nord de la ville.

When you express purpose with an infinitive, French needs pour + infinitive, not just the bare infinitive.

Could I say Je prends un taxi pour le nord de la ville and drop aller?

You can, but the nuance changes slightly.

Je prends un taxi pour aller au nord de la ville.
→ focuses on your action of going to the north of the city.
Je prends un taxi pour le nord de la ville.
→ sounds more like a taxi bound for the north of the city (the destination is attached to the taxi).

In real life:

To a taxi dispatcher: Un taxi pour le nord de la ville, s’il vous plaît. – “A taxi for the north of the city, please.”
In a neutral description, pour aller is a bit clearer and more typical.

What exactly is au in au nord?

Au is the contraction of à + le:

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

Because nord is masculine singular (le nord), you get:

à le nord → au nord

So au nord de la ville literally means at/to the north of the city.

Why is it au nord de la ville and not dans le nord de la ville? Is there a difference?

There is a nuance:

au nord de la ville
Traditionally: to the north of the city, i.e. outside or beyond the city, on its northern side.
Example: a village located north of the city on a map.
dans le nord de la ville
In the north of the city, i.e. inside the city, in its northern neighbourhoods.

In everyday speech, many people do not respect the distinction strictly, but:

Talking about neighbourhoods within the city → dans le nord de la ville is more precise.
Talking about a place located beyond the city limits → au nord de la ville fits better.

Your sentence is compatible with both interpretations in casual speech.

Why do we say de la ville and not de ville?

In French, common concrete nouns normally take an article (le, la, les, un, une, des) even when English has no article.

Here:

la ville = the city
de la ville = of the city / from the city

De ville without an article would sound wrong in this context.

Compare:

au nord de Paris (Paris is a proper noun, no article)
au nord de la ville (common noun, needs an article)

Can I just say Je prends un taxi pour aller au nord and omit de la ville?

Yes, if the context makes it clear which place you mean.

Je prends un taxi pour aller au nord.
→ I’m taking a taxi to go north.

This is more general (just “to the north”). Adding de la ville specifies that you mean “to the north of the city” (or the northern part of that city).

Why is the present tense Je prends used, and not a future tense like Je prendrai?

French often uses the present tense for near-future actions, especially when the plan is already decided:

Je prends un taxi can mean:
- I’m taking a taxi (right now), or
- I’m going to take a taxi (very soon / that’s my plan).

If you say Je prendrai un taxi, it sounds a bit more distant, like a statement of future intention or prediction, often less immediate or more formal.

For most everyday plans, present tense = “I’m going to …” in English.

How do you pronounce prends in Je prends? Do you say the d and s?

Prends is pronounced [prɑ̃] in IPA (roughly “pron” in English without the final n).

The final d and s are silent.
Nasal vowel en / an → mouth open, air passing through the nose.

So:

Je prends sounds like [ʒə prɑ̃], not like “prehndz”.

How would you say this sentence in the negative?

The normal negative form is:

Je ne prends pas de taxi pour aller au nord de la ville.
→ I’m not taking a taxi to go to the north of the city.

Notice:

ne … pas around the verb: ne prends pas
un taxi becomes de taxi after pas (this happens with most indefinite articles in the negative: un / une / des → de).