Learn Hardcore French: À l'ouest, le soleil se couche sur la mer.

In French, the preposition à is normally used with the four cardinal directions (à l’est, à l’ouest, au nord, au sud) when you mean “in the direction of / in the west / to the west.”

À l’ouest = in the west / to the west (as a general direction or area)
Dans l’ouest = inside the western part of something specific (e.g. dans l’ouest de la France = in the west of France)

En l’ouest is simply not idiomatic in modern French; you’d say dans l’ouest or à l’ouest depending on the nuance.

Why is there an apostrophe in l'ouest instead of la ouest or le ouest?

French has an elision rule: when a word ending in a vowel (le, la, de, ne, que, je, me, etc.) comes directly before a word beginning with a vowel or mute h, the vowel is dropped and replaced with an apostrophe.

le ouest → l’ouest
la ouest → l’ouest

You can’t see the gender from the article here; you just get l’ouest. (Grammatically, ouest is masculine: l’ouest, un ouest.) The apostrophe makes pronunciation smoother: you say [lust] rather than something like [lə uɛst].

Why is there a comma after À l'ouest?

À l’ouest is an adverbial phrase (it tells you where). In French, when you place such a phrase at the beginning of the sentence for emphasis or style, it’s common (though not absolutely mandatory) to separate it with a comma:

Le soleil se couche à l’ouest.
À l’ouest, le soleil se couche. (fronted for emphasis, with a comma)

So the comma just marks that À l’ouest has been moved to the front; it doesn’t change the grammar or meaning.

Why is it le soleil and not just soleil without an article?

In French, common nouns almost always need an article, even when English can drop it.

English: “Sun sets in the west.” / “Sunlight is warm.”
French: Le soleil se couche à l’ouest. / La lumière du soleil est chaude.

Here le soleil has a general meaning (“the sun” as a unique object). French uses the definite article le for general truths, like:

La Terre tourne autour du soleil.
L’eau bout à 100 degrés.

What does se couche literally mean, and why is it reflexive?

The verb is se coucher, which is reflexive. Literally it means “to lie down, to go to bed”.

Je me couche à onze heures. = I go to bed at eleven.

By extension, le soleil se couche literally suggests “the sun lies down”. Idiomatically, this is how French says “the sun sets.”

So:

coucher = to lay/put something down (transitive)
- Je couche le bébé. = I put the baby to bed.
se coucher = to lie down / to go to bed (reflexive, subject does it to itself)
- Je me couche. = I go to bed.
- Le soleil se couche. = The sun sets.

Is se coucher only used for the sun, or also for people?

It’s used for both:

For people/animals: se coucher = to lie down / go to bed
- Je me couche tôt. = I go to bed early.
- Le chien se couche sur le tapis. = The dog lies down on the rug.
For the sun: le soleil se couche is the standard way to say “the sun sets.”

Context usually makes it clear which meaning you want.

What is the difference between se coucher and coucher de soleil?

Two different things:

Se coucher (verb): “to set” (for the sun), “to go to bed” (for people)
- Le soleil se couche. = The sun sets.
Un coucher de soleil (noun phrase): “a sunset”
- J’aime regarder le coucher de soleil. = I like watching the sunset.

So se coucher is an action (verb), coucher de soleil is the event/phenomenon as a thing (noun).

Why is the present tense used in le soleil se couche? Is it a specific time or a general fact?

French present tense (le soleil se couche) can express:

A general truth / habitual fact:
- Le soleil se couche à l’ouest. = The sun sets in the west (always, as a fact of nature).
A present-time description (depending on context):
- Regarde, le soleil se couche. = Look, the sun is setting.

In your sentence, with no context, it’s most naturally understood as a general fact about the world, like in English “The sun sets in the west.”

Why is it sur la mer and not dans la mer or au-dessus de la mer?

Each preposition gives a slightly different image:

sur la mer: literally “on the sea,” but here it means “over the sea / above the surface of the sea.” It’s the most natural, idiomatic choice in this poetic/descriptive sentence.
dans la mer: “in the sea” (inside the water)
- You’d use this for something physically in the water:
  - Les poissons nagent dans la mer.
au-dessus de la mer: “above the sea” (more spatial/technical)
- L’hélicoptère vole au-dessus de la mer.

For a sunset over the sea, French typically says sur la mer.

Why do we say la mer and not something like mer without an article?

Again, French almost always needs an article with common nouns.

la mer = the sea (as a general concept, or a specific sea, depending on context)
English can say “at sea,” “over sea,” etc. with no article, but French normally cannot.

Compare:

J’aime la mer. = I like the sea.
Nous habitons près de la mer. = We live near the sea.

Dropping the article (*j’aime mer) is incorrect in standard French.

How do you pronounce À l'ouest, le soleil se couche sur la mer?

In IPA (standard French):

À l’ouest → /a lwɛst/
le soleil → /lə sɔ.lɛj/
se couche → /sə kuʃ/
sur la mer → /syʁ la mɛʁ/

Full sentence: /a lwɛst, lə sɔ.lɛj sə kuʃ syʁ la mɛʁ/

Notes:

l’ouest is one syllable: lwɛst.
Final -t in ouest is pronounced.
Final -r in mer is pronounced (French /ʁ/).

Is ouest capitalized here? What’s the rule?

In your sentence, ouest is not a proper name; it’s a simple direction, so it’s normally lowercase in French:

à l’ouest, à l’est, au nord, au sud

You might see a capital letter when it’s part of a proper noun or a geopolitical concept:

L’Extrême-Orient, le Moyen-Orient
l’Ouest vs l’Est as political blocs in some contexts

But in À l’ouest, le soleil se couche sur la mer, it should be ouest with a lowercase o.