Le ski est difficile.

In French, general statements about activities or sports often use the definite article.

So le ski means skiing or the sport of skiing in a general sense.

• Le ski est difficile. = Skiing is difficult.
• J’aime le ski. = I like skiing.

English often drops the article in these cases, but French usually keeps it.

Here, ski means the sport/activity of skiing.

French can also use un ski to mean a ski (the piece of equipment), but in le ski est difficile, the meaning is clearly the sport.

So:

• le ski = skiing / the sport of skiing
• un ski = a ski

Yes. Ski is a masculine noun in French, so it takes le in the singular:

• le ski

If you were talking about several skis, you would say:

• les skis

Even when le ski means skiing as a sport, it still keeps its grammatical gender, which is masculine.

Because difficile is not directly describing the noun inside the noun phrase. It is part of the sentence with the verb être.

The structure is:

• Le ski = subject
• est = verb
• difficile = adjective describing the subject after être

This is very normal in French:

• Le livre est intéressant.
• La soupe est chaude.
• Le ski est difficile.

After être, adjectives usually come after the verb, just like in English: is difficult.

It actually agrees with ski, but in this case the masculine singular and feminine singular forms look the same.

Since ski is masculine singular, the adjective is also masculine singular:

• Le ski est difficile.

But difficile is one of those adjectives whose masculine and feminine singular forms are identical:

• masculine singular: difficile
• feminine singular: difficile

You only clearly see a spelling change in the plural:

• Les sports d’hiver sont difficiles.

A simple pronunciation guide is:

luh skee eh dee-fee-seel

More approximately in IPA:

/lə ski ɛ di.fi.sil/

A few notes:

• le is pronounced softly, like luh
• ski sounds very close to English ski
• est here sounds like eh
• difficile has three clear parts: di-fi-cile

Est is just the verb is.
Here the sentence is a straightforward subject + verb + adjective structure:

• Le ski est difficile.
• Skiing is difficult.

You can also hear:

• Le ski, c’est difficile.

That version is also natural, but it has a slightly different feel. It sounds more like: As for skiing, it’s difficult or Skiing, that’s difficult.

So:

• Le ski est difficile = plain, direct statement
• Le ski, c’est difficile = a bit more conversational or emphatic

Yes, absolutely.

• Le ski est difficile.
• Faire du ski est difficile.

Both are correct, but they are a little different in focus:

• Le ski est difficile = skiing as a sport is difficult
• Faire du ski est difficile = doing/going skiing is difficult

The first is more general and compact. The second highlights the action more clearly.

This is a very common difference between English and French.

English often uses the -ing form for activities:

• Skiing is difficult
• Swimming is fun
• Reading is useful

French often uses a noun with the definite article instead:

• Le ski est difficile
• La natation est amusante
• La lecture est utile

So even though le usually translates as the, in sentences like this it is often best understood as part of the normal French way to talk about activities in general.

You can definitely use other adjectives, depending on the meaning you want:

• Le ski est difficile. = Skiing is difficult.
• Le ski est dangereux. = Skiing is dangerous.
• Le ski est amusant. = Skiing is fun.
• Le ski est passionnant. = Skiing is exciting.

So the sentence pattern is very useful:

Le/Lа + activity + est + adjective

It is a basic and common way to describe sports, hobbies, and activities in French.