Βάλε το γάλα στο ψυγείο, μη χαλάσει.

Βάλε means put. It is the singular imperative form of βάζω (to put / to place).

So:

• βάζω = I put / I am putting
• βάλε = put! (said to one person)

In this sentence, Βάλε το γάλα στο ψυγείο means Put the milk in the fridge.

Because the sentence is giving a command to one person.

• βάζεις = you put / you are putting (statement, not command)
• βάζετε = you put / you are putting, or put! to more than one person / polite singular
• βάλε = put! to one person, informal

So:

• Βάλε το γάλα... = Put the milk... (to one person)
• Βάλτε το γάλα... = Put the milk... (to more than one person, or polite)

στο is a contraction of σε + το.

• σε = in / to / at
• το = the (neuter singular)

So:

• σε το ψυγείο → στο ψυγείο

This contraction is completely standard in modern Greek.

Examples:

• στο σπίτι = in the house / at home
• στο αυτοκίνητο = in the car
• στο ψυγείο = in the fridge

Because both nouns are neuter singular nouns.

• το γάλα = the milk
• το ψυγείο = the fridge

In Greek, the article agrees with the noun in gender, number, and case. Here both nouns are neuter singular, so they both take το.

Also:

• γάλα is the direct object of βάλε
• ψυγείο comes after στο (= σε + το), so the article is built into that form

Literally, it means something like so that it doesn’t spoil or lest it spoil.

The verb χαλάω / χαλώ can mean several things depending on context, such as:

• to break
• to ruin
• to spoil / go bad

With food, χαλάσει usually means go bad / spoil.

So μη χαλάσει here means:

• so it won’t spoil
• so that it doesn’t go bad

Because μη is used for negation in contexts like:

• commands
• prohibitions
• wishes
• subordinate clauses with subjunctive-like meaning

δεν is used mainly for straightforward statements of fact.

Compare:

• Δεν χαλάει. = It is not spoiling / It doesn’t spoil.
  (plain statement)
• Μη χαλάσει. = So that it doesn’t spoil / lest it spoil.
  (not a plain statement; this is a purpose/result-style idea after a command)

So μη is the correct negative word here.

χαλάσει is the aorist subjunctive form of χαλάω / χαλώ.

In this sentence, it expresses a single event or the idea of ending up spoiled, rather than an ongoing process.

That is why Greek uses the aorist form here:

• μη χαλάσει = so that it doesn’t spoil / so it won’t go bad

This is very common after commands when Greek expresses purpose or prevention.

That is a very natural question, because learners often expect να with the subjunctive.

A fuller version could be:

• Βάλε το γάλα στο ψυγείο, για να μη χαλάσει.
• Βάλε το γάλα στο ψυγείο να μη χαλάσει.

But Greek often omits words in short, natural speech when the meaning is obvious. So:

• Βάλε το γάλα στο ψυγείο, μη χαλάσει.

is a compact, natural way to say:

• Put the milk in the fridge, so it doesn’t spoil.

So yes, you can think of this as a shortened form where the idea of so that is understood.

The comma separates the main command from the explanatory/purpose part.

• Βάλε το γάλα στο ψυγείο = main command
• μη χαλάσει = reason/purpose/result idea: so it doesn’t spoil

In English, we often do something similar:

• Put the milk in the fridge, so it doesn’t spoil.

The comma helps show that the second part is not a separate full sentence, but an added explanation.

No, it is understood from context.

In μη χαλάσει, the implied subject is the milk.

Greek often leaves subjects unstated when they are clear from the situation. So Greek does not need to say:

• ...μη χαλάσει το γάλα

because το γάλα has already been mentioned, and the listener easily understands it.

Yes, absolutely. That is a very clear and natural version.

Compare:

• Βάλε το γάλα στο ψυγείο, μη χαλάσει.
  More compact, slightly more elliptical
• Βάλε το γάλα στο ψυγείο για να μη χαλάσει.
  More explicit: Put the milk in the fridge so that it doesn’t spoil

Both are correct. The version with για να may feel easier for learners because the purpose relationship is stated more directly.

Yes, Greek word order is fairly flexible, although some orders sound more natural than others.

The given sentence is very natural:

• Βάλε το γάλα στο ψυγείο, μη χαλάσει.

You could also hear:

• Βάλε στο ψυγείο το γάλα, μη χαλάσει.

This changes the emphasis slightly, but the meaning stays the same.

Still, for a learner, the original order is a very good default: verb + object + place.

Yes, in this sentence το ψυγείο means the fridge / refrigerator.

The word comes from the idea of cooling, and in everyday Greek it is the normal word for a household refrigerator.

So:

• στο ψυγείο = in the fridge

No. χαλάω / χαλώ is a very common verb with several meanings, depending on context.

It can mean:

• to spoil / go bad
  
  • Το γάλα χάλασε. = The milk went bad.
• to break / stop working
  
  • Χάλασε το αυτοκίνητο. = The car broke down.
• to ruin / mess up
  
  • Μου χάλασες τη μέρα. = You ruined my day.

So in this sentence, because the topic is milk, the meaning is clearly spoil / go bad.

It is informal because of Βάλε, which is the singular informal imperative.

If you wanted to say the same thing politely or to more than one person, you would say:

• Βάλτε το γάλα στο ψυγείο, μη χαλάσει.

So:

• βάλε = informal singular
• βάλτε = plural or polite singular

The rest of the sentence stays the same.