Learn Hardcore French: Marie aime les nuances de la langue, alors elle se concentre sur chaque détail. - Marie likes the nuances of the language, so she focuses on every detail.

Marie = 3rd person singular (she)
Present tense of aimer:
- j’aime
- tu aimes
- il/elle/on aime
- nous aimons
- vous aimez
- ils/elles aiment

Since Marie = elle, you must use aime:

Marie aime les nuances de la langue.
Marie likes the subtleties of the language.

Why is it les nuances and not just nuances or des nuances?

French usually needs an article (definite or indefinite) before a noun, even when English doesn’t.

les nuances = the nuances/subtleties (all of them, in general)
des nuances = some nuances (an unspecified number)
Bare nuances (with no article) is normally incorrect in this context.

Here, les nuances de la langue means she appreciates the subtleties of language in general, not just some specific nuances. So the definite article les is appropriate.

What does de la langue mean exactly, and why not just de langue?

De la langue literally means “of the language”.

de + la + langue → de la langue (of the language)

You might see de langue in other contexts (for example, un cours de langue = a language course), but when we’re talking about the nuances of a specific thing in general, French normally keeps the definite article:

les nuances de la langue = the nuances of the language (as a whole system)
If you said les nuances de langue, it would sound incomplete or odd here.

You could be more specific and say:

les nuances de la langue française = the nuances of the French language.

Why is alors used here, and could I use donc instead?

In this sentence, alors means “so” / “therefore” and introduces a consequence:

Marie aime les nuances de la langue, alors elle se concentre sur chaque détail.
= Marie likes the subtleties of the language, so she focuses on every detail.

You could also use donc here:

Marie aime les nuances de la langue, donc elle se concentre sur chaque détail.

Differences:

alors is very common in spoken French and can sound slightly more informal or narrative.
donc is also very common; in writing it can sound a bit more neutral or logical.

Both are correct in this sentence.

Why do we say elle se concentre and not just elle concentre?

Se concentrer is a reflexive verb in French, meaning “to concentrate / to focus (oneself).”

se concentrer = to focus, to concentrate
concentrer (without se) is a different verb and usually means “to concentrate something” (like a liquid, energy, resources), which is rare in everyday speech.

So:

Elle se concentre sur chaque détail.
= She concentrates on every detail.

If you said elle concentre sur…, it would be wrong; this verb almost always needs the reflexive pronoun se when it means “to focus.”

Why is the preposition sur used in se concentrer sur chaque détail, and not à or dans?

With se concentrer, the usual preposition for the object of focus is sur:

se concentrer sur quelque chose = to focus on something

Examples:

Je me concentre sur mon travail.
Ils se concentrent sur l’examen.

Using à or dans would be incorrect here:

✗ se concentrer à chaque détail
✗ se concentrer dans chaque détail

So se concentrer sur chaque détail is the natural, idiomatic structure.

Why is it chaque détail without an article (no le or un)?

The determiner chaque (each / every) is always used without another article in front of the noun:

chaque détail = each detail / every detail
chaque jour = every day
chaque personne = each person

You cannot say:

✗ le chaque détail
✗ un chaque détail

So the correct structure is always chaque + singular noun.

Is détail masculine or feminine, and how can I see that in this sentence?

Détail is a masculine noun: un détail, le détail.

In this sentence, you don’t directly see the gender because:

chaque doesn’t change form with gender (it’s the same for masculine and feminine).
There is no article like le or un before it.

You just have to know from vocabulary that:

un détail (masculine)
la langue (feminine)

Why is elle repeated after the comma? In English we might say “Marie likes… and focuses…” without repeating “she.”

In French, you must have a subject pronoun for each clause; it’s not normally dropped.

Marie aime les nuances de la langue, alors elle se concentre sur chaque détail.

If you removed elle, the second clause would be ungrammatical:

✗ Marie aime les nuances de la langue, alors se concentre sur chaque détail.

So even though English can omit the second “she” (Marie likes… and focuses…), French keeps elle.

Could I say Marie adore les nuances de la langue instead of Marie aime? Is there a difference?

Yes, you can say Marie adore les nuances de la langue, but the nuance changes:

aimer = to like / to love (context decides how strong it is)
adorer = to adore / to really love (stronger enthusiasm)

So:

Marie aime les nuances de la langue
= She likes / loves the nuances of the language.
Marie adore les nuances de la langue
= She is really passionate about them; it sounds stronger and more enthusiastic.