Paul préfère la course à pied, alors que Marie aime la natation.

In French, when you talk about sports or activities in general, you usually use the definite article: le, la, or les.

So:

• Paul préfère la course à pied
• Marie aime la natation

This is very normal in French, even though English usually says just running and swimming without the.

You see the same pattern in:

• J’aime le tennis.
• Elle préfère la danse.
• Nous adorons le ski.

Course by itself can mean several things, such as a race, a run, or even shopping/errands in some contexts.

La course à pied is more specific: it means running as a sport or physical activity, literally running on foot.

So à pied helps make the meaning clear.

Compare:

• une course = a race / a run / an errand, depending on context
• la course à pied = running

À pied literally means on foot.

In la course à pied, it helps distinguish ordinary human running from other kinds of racing or movement. It is a fixed expression.

You will also see à pied in other common phrases:

• aller à pied = to go on foot
• faire le trajet à pied = to do the trip on foot

The two verbs do not mean exactly the same thing:

• préférer = to prefer / to like better
• aimer = to like / to love

So the sentence is not perfectly parallel in meaning:

• Paul prefers running
• Marie likes swimming

That may simply be a stylistic choice. French often varies verbs to avoid repetition.

If you wanted a more exact parallel structure, you could also say:

• Paul préfère la course à pied, alors que Marie préfère la natation. or
• Paul aime la course à pied, alors que Marie aime la natation.

Yes, aimer can mean both to like and to love. The meaning depends on context.

With activities, objects, and hobbies, it often means to like:

• J’aime le café.
• Elle aime danser.

With people, it can mean to love:

• Il aime Marie.

So in Marie aime la natation, it clearly means Marie likes swimming.

This is a spelling change that happens in many forms of préférer.

The infinitive is:

• préférer

But in the present tense, the first é often changes to è in forms where the next syllable contains a silent e:

• je préfère
• tu préfères
• il/elle préfère
• ils/elles préfèrent

But:

• nous préférons
• vous préférez

This is part of a common French verb pattern. The accent change also reflects pronunciation.

Alors que means whereas, while, or while on the other hand. It introduces a contrast between two full ideas.

So:

• Paul préfère la course à pied, alors que Marie aime la natation.

This sounds a bit more structured and explicit than using mais.

If you used mais, the sentence would still be understandable:

• Paul préfère la course à pied, mais Marie aime la natation.

However, alors que is especially good when you want to highlight a contrast between two people, situations, or preferences.

No. In this sentence, alors que is followed by the indicative, not the subjunctive.

That is because it is simply presenting a contrast between two facts:

• Paul préfère...
• Marie aime...

So Marie aime is completely normal.

Yes, absolutely.

You could say:

• Paul préfère courir, alors que Marie aime nager.

That version uses verbs and sounds a bit more direct and conversational.

The original sentence uses nouns:

• la course à pied
• la natation

This sounds slightly more like talking about sports or activities as categories.

Both are correct; the choice depends on style.

When préférer means to prefer something, it can take the thing directly:

• Paul préfère la course à pied.
• Je préfère le thé.

No preposition is needed there.

But if you compare one thing to another, French can use à:

• Paul préfère la course à pied à la natation.

So in your sentence, there is no preposition after préfère because the comparison is expressed in a separate clause with alors que Marie aime la natation.

Because both nouns are feminine:

• la course = feminine
• la natation = feminine

The article matches the gender of the noun.

A useful point: the gender comes from the noun itself, not from the fact that it is a sport. Different sports can have different genders:

• le tennis
• le football
• la natation
• la danse

So you need to learn the article together with the noun whenever possible.