Paul vide la soucoupe de peur que l’eau y reste.

De peur que is a conjunction meaning for fear that or out of fear that.

It introduces something the subject wants to avoid. In this sentence, Paul empties the saucer because he is afraid of one possible result: that the water might stay in it.

It is a fairly formal expression. In everyday French, people also often use:

• de peur de + infinitive when the subject stays the same
• other more common turns such as pour éviter que...

So here, de peur que l’eau y reste means something like for fear that the water may remain there.

Because de peur que normally requires the subjunctive.

The subjunctive is used after expressions involving:

• fear
• emotion
• doubt
• uncertainty
• intention
• possibility rather than a stated fact

Here, the water staying in the saucer is not presented as a fact. It is something Paul fears might happen. That is why French uses:

• que l’eau y reste not
• que l’eau y reste in the indicative

In form, reste is the present subjunctive of rester.

Yes, very often you will see:

• de peur que l’eau n’y reste

This ne is called the expletive ne. It does not make the clause negative.

So:

• de peur que l’eau y reste
• de peur que l’eau n’y reste

can both mean the same thing here: for fear that the water might remain there.

A learner often expects ne to mean not, but in this construction it is just a stylistic/grammatical marker, especially in more formal French. In modern everyday usage, it is often left out, which is what has happened in your sentence.

Y is an adverbial pronoun that usually means there or in it / in that place, depending on context.

Here, y refers back to la soucoupe.

So:

• l’eau y reste = the water remains there / in it

French often uses y instead of repeating the noun:

• dans la soucoupe → y

This is very natural French. English sometimes keeps the noun or says in it, while French often prefers y.

Because eau begins with a vowel sound.

In French, le or la usually becomes l’ before a vowel or mute h:

• la table
• l’eau
• l’école
• l’homme

So la eau is not possible. It must be l’eau.

Here, vide is the verb vider in the present tense, third person singular:

• je vide
• tu vides
• il/elle/on vide

So:

• Paul vide la soucoupe = Paul empties the saucer

It is easy to confuse this with the adjective vide, which means empty:

• La soucoupe est vide = The saucer is empty

In your sentence, it is clearly the verb because it has a direct object:

• vide la soucoupe

French uses articles much more often than English does.

Where English can sometimes say:

• Paul empties saucer — though this sounds unnatural in English too

French normally needs an article:

• Paul vide la soucoupe

Here la means the, referring to a specific saucer. In ordinary French, bare nouns without an article are much less common than in English.

It can mean either, depending on how you want to translate it.

• rester = to stay, to remain

In this sentence, both are possible in English:

• for fear that the water stays in it
• for fear that the water remains in it

Remain sounds a little more formal and often fits well with this kind of sentence. Stay is more everyday English.

French often uses the present subjunctive after conjunctions like de peur que, even when English might naturally think of a future idea.

The feared event is something that could happen after Paul empties the saucer, but French does not need a separate future form here. The conjunction plus the subjunctive already expresses that it is a possible, not-yet-realized event.

So French says:

• de peur que l’eau y reste

where English might think:

• for fear that the water will stay there
• for fear that the water might remain there

French simply handles that idea differently.

Yes. De peur que is correct, but it is somewhat formal or literary.

More everyday alternatives might be:

• Paul vide la soucoupe pour que l’eau n’y reste pas.
• Paul vide la soucoupe pour éviter que l’eau y reste.

These mean roughly:

• Paul empties the saucer so that the water doesn’t stay in it
• Paul empties the saucer to avoid the water staying in it

Your original sentence is perfectly good French, but a learner should know that native speakers may often choose a more straightforward phrasing in conversation.

No, the word order is normal.

The clause is built like this:

• que
  • subject + pronoun + verb

So:

• que = that
• l’eau = the subject
• y = there / in it
• reste = stays/remains

This gives:

• que l’eau y reste

French object and adverbial pronouns like y usually come before the conjugated verb, which is why it appears before reste.