Ne casse pas ce verre.

Because Ne casse pas ce verre. is in the imperative, which is the form used for commands, instructions, and requests.

In French imperatives, you normally do not use the subject pronoun:

• Casse ce verre. = Break this glass.
• Ne casse pas ce verre. = Don’t break this glass.

The hidden subject here is tu, so this is a command directed at one person informally.

In French negation, ne ... pas goes around the verb.

So:

• casse = break
• ne casse pas = do not break

This is the normal pattern for a negative imperative:

• Ne parle pas. = Don’t speak.
• N’ouvre pas la porte. = Don’t open the door.
• Ne casse pas ce verre. = Don’t break this glass.

So ne comes before the verb, and pas comes after it.

Casse is the tu imperative form of the verb casser.

The verb casser means to break.
Its tu imperative form is:

• casse

So:

• Casse ce verre. = Break this glass.
• Ne casse pas ce verre. = Don’t break this glass.

For most -er verbs, the tu imperative looks like the tu present tense form, but without the final -s:

• tu casses → casse !
• tu parles → parle !
• tu fermes → ferme !

Because with most -er verbs, the tu form of the imperative drops the final -s.

Examples:

• tu parles → Parle !
• tu regardes → Regarde !
• tu casses → Casse !

So casse is correct.

A useful note: the -s may reappear before y or en for pronunciation reasons:

• Vas-y !
• Manges-en !

But in Ne casse pas ce verre, there is no -s.

Ce here means this or that, depending on context.

Before a masculine singular noun, French often uses:

• ce
  • masculine singular noun

So:

• ce verre = this glass / that glass

French does not always distinguish this and that as clearly as English does. If someone wants to be more specific, they can say:

• ce verre-ci = this glass
• ce verre-là = that glass

But in normal speech, ce verre is very common.

Because verre is a masculine singular noun that begins with a consonant sound.

French uses:

• ce before masculine singular nouns beginning with a consonant sound
• cet before masculine singular nouns beginning with a vowel or mute h

So:

• ce verre = this glass
• cet arbre = this tree
• cet homme = this man

Since verre starts with the consonant sound v, ce is correct.

Verre is masculine.

So you say:

• ce verre
• un verre
• le verre

Not:

• cette verre
• une verre

This matters because demonstratives, articles, and adjectives often have to agree with the noun.

A careful pronunciation is approximately:

nuh kass pah suh vair

More naturally in French:

• ne is often light and reduced
• casse sounds like kass
• pas sounds like pah
• ce sounds like suh
• verre sounds like vair

A rough IPA version is:

/nə kas pa sə vɛʁ/

A few pronunciation notes:

• The e in ne and ce is often weak.
• verre does not sound like English very.
• The final r in verre is the French r, produced in the back of the throat.

In careful or formal French, yes, you would say Ne casse pas ce verre.

In everyday spoken French, many speakers drop ne and say:

• Casse pas ce verre.

This is very common in conversation, but learners should still learn the full standard form:

• Ne casse pas ce verre.

That is the form expected in writing and in careful speech.

It can be either, depending on context and tone.

Ne casse pas ce verre. can sound like:

• a direct command: Don’t break this glass.
• a warning: Be careful not to break this glass.
• a request: Please don’t break this glass.

French imperatives do not automatically show politeness the way English sometimes does with please. Tone of voice and situation matter a lot.

If you want to make it more polite, you could say:

• Ne casse pas ce verre, s’il te plaît.

Yes. If you are speaking to one person informally, you use:

• Ne casse pas ce verre.

If you are speaking to one person formally or to several people, you use the vous imperative:

• Ne cassez pas ce verre.

So the difference is:

• Ne casse pas... = don’t break... (tu)
• Ne cassez pas... = don’t break... (vous)

Yes, but casser is the more common everyday verb for to break.

• Ne casse pas ce verre. = the normal, natural everyday phrasing

Briser also means to break, but it can sound more literary, dramatic, or specific depending on context.

So in ordinary speech, casser is usually the best choice here.

It can mean both, depending on context.

• un verre = a glass, a drinking glass
• le verre = glass, the material

In Ne casse pas ce verre, the most natural meaning is this glass as an object, probably a drinking glass.

French often relies on context to make the meaning clear.