Μην δαγκώνεις το μολύβι σου, θα το χαλάσεις.

Because μην is used for negative commands and other subjunctive-type constructions, while δεν is used to negate statements.

• Δεν δαγκώνεις το μολύβι σου = You are not biting your pencil / You don’t bite your pencil
• Μην δαγκώνεις το μολύβι σου = Don’t bite your pencil

So in this sentence, μην shows that the speaker is telling someone not to do something.

It looks like the 2nd person singular present form, but after μην it functions as part of a negative command.

So μην δαγκώνεις means something like:

• don’t be biting
• don’t keep biting
• don’t bite

The ending -εις shows that the speaker is talking to one person in an informal singular way.

This is a very common Greek aspect question.

• Μην δαγκώνεις = don’t bite / don’t keep biting / don’t chew on it
• Μην δαγκώσεις = don’t bite it even once

So:

• δαγκώνεις is imperfective: it focuses on an ongoing, repeated, or habitual action
• δαγκώσεις is perfective: it focuses on a single completed action

In this sentence, Μην δαγκώνεις το μολύβι σου sounds natural because the idea is that someone is chewing on or gnawing at the pencil.

In Greek, possessive words like μου, σου, του, της often come after the noun.

So:

• το μολύβι σου = your pencil
• literally: the pencil your

This is completely normal Greek word order.

A more emphatic version would be:

• το δικό σου μολύβι = your pencil / the pencil that is yours

But in ordinary speech, το μολύβι σου is the standard way to say it.

Because Greek often drops subject pronouns when they are not needed.

The verb ending already tells you who the subject is:

• δαγκώνεις = you bite
• χαλάσεις = you will ruin

So Greek does not need to say εσύ unless it wants emphasis or contrast.

For example:

• Μην δαγκώνεις το μολύβι σου = normal
• Εσύ μην δαγκώνεις το μολύβι σου = more emphatic, like you don’t bite your pencil

That το means it.

It refers back to το μολύβι.

So:

• θα το χαλάσεις = you will ruin it

In Greek, weak object pronouns usually come before the verb:

• το βλέπω = I see it
• θα το χαλάσεις = you will ruin it

Since μολύβι is neuter singular, the pronoun is το.

Here χαλάσεις means you will ruin it, damage it, or mess it up.

The verb is χαλάω / χαλώ, which can mean things like:

• ruin
• spoil
• damage
• break depending on context

In this sentence, it does not necessarily mean the pencil will snap in half. It more generally means that by biting it, you will damage it.

In Modern Greek, the future is usually formed with θα + verb.

So:

• θα χαλάσεις = you will ruin
• θα το χαλάσεις = you will ruin it

Greek does not usually have a separate future tense ending the way some languages do. Instead, θα marks the future.

In this sentence, the second clause gives the result/consequence of the first one:

• Don’t bite your pencil, you’ll ruin it.

Because Greek, like English, can link a warning and its consequence with a simple comma.

So this structure is natural:

• Μην δαγκώνεις το μολύβι σου, θα το χαλάσεις.

It works like:

• Don’t do that, you’ll regret it.
• Don’t touch it, you’ll break it.

You could express the relationship more explicitly in other ways, but the comma version is very normal and natural.

You would use the plural/formal verb forms:

• Μην δαγκώνετε το μολύβι σας, θα το χαλάσετε.

Changes:

• δαγκώνεις → δαγκώνετε
• σου → σας
• χαλάσεις → χαλάσετε

In Greek, the plural form is also used for formal singular speech, like French vous or Spanish usted/ustedes patterns.