Не мочи телефон, иначе он перестанет работать.

Here мочить means to make wet / to get something wet. So Не мочи телефон means Don’t get the phone wet.

The form мочи is the imperative singular of мочить, used when speaking to one person informally.

• мочить = to wet, to soak, to make wet
• мочи! = wet it! / make it wet!
• не мочи! = don’t wet it!

In everyday Russian, this is a natural way to warn someone not to expose an object to water.

Russian usually forms negative informal commands with:

не + imperative

So:

• мочи = wet it
• не мочи = don’t wet it

That is the normal pattern.

Compare:

• Читай. = Read.
• Не читай. = Don’t read.
• Трогай. = Touch it.
• Не трогай. = Don’t touch it.

So Не мочи телефон is structurally very straightforward: Don’t get the phone wet.

This is a very common learner question. In Russian commands, the imperfective is often used in negative instructions when the speaker means don’t do that at all or avoid that action.

So Не мочи телефон sounds like a general warning: Don’t get the phone wet.

A perfective negative imperative can sound more like don’t let a single completed instance happen, but in many everyday warnings Russian often prefers the imperfective.

Here the imperfective works well because the idea is general and preventive.

Телефон is in the accusative case, because it is the direct object of мочи.

The infinitive is мочить что? = to wet what?

So:

• мочить телефон = to get the phone wet
• Не мочи телефон = Don’t get the phone wet

Because телефон is an inanimate masculine noun, its accusative singular looks exactly like the nominative singular:

• nominative: телефон
• accusative: телефон

So the form does not change.

Иначе means otherwise or or else.

So the sentence structure is:

• Не мочи телефон = Don’t get the phone wet
• иначе = otherwise / or else
• он перестанет работать = it will stop working

Together:

Don’t get the phone wet, otherwise it will stop working.

It is a very common linking word in warnings and advice.

Examples:

• Спеши, иначе опоздаешь. = Hurry, otherwise you’ll be late.
• Надень куртку, иначе замёрзнешь. = Put on a jacket, otherwise you’ll get cold.

In Russian, nouns have grammatical gender, and pronouns agree with that gender.

Телефон is a masculine noun, so the matching pronoun is он, which literally means he, but for objects it is translated as it in English.

So:

• телефон = masculine
• он = the pronoun that agrees with телефон

That is why он перестанет работать means it will stop working, not he will stop working.

Russian often expresses to stop doing something with:

перестать + infinitive

So:

• перестать работать = to stop working
• он перестанет работать = it will stop working

Here:

• перестанет is the future form of перестать
• работать is the infinitive to work

This is very normal Russian.

Other examples:

• Он перестал курить. = He stopped smoking.
• Машина перестала ехать. = The car stopped moving.
• Телефон перестанет работать. = The phone will stop working.

Because the sentence describes a consequence that will happen after the phone gets wet.

The logic is:

• If you get the phone wet now,
• then later it will stop working.

So Russian uses the future:

• перестанет = will stop

This matches English very closely in this kind of warning.

Перестанет comes from перестать, which is a perfective verb.

Perfective verbs in Russian often express a single complete event or change. Here the change is:

the phone stops functioning

That is a completed transition, so the perfective makes sense.

Because perfective verbs do not have a present tense in the normal sense, forms like перестанет are interpreted as future:

• перестанет = will stop

Grammatically, yes, because мочить can mean to wet or to soak, but in this context Don’t get the phone wet is the best natural translation.

Don’t soak the phone sounds stronger in English, as if someone might deliberately immerse it in water. The Russian sentence is broader and more practical: any wetting is bad.

So the best English sense is:

Don’t get the phone wet.

It is informal singular, because мочи is used when speaking to one person in an informal way.

If you wanted the formal singular or plural version, you would say:

Не мочите телефон, иначе он перестанет работать.

So:

• не мочи = don’t get it wet, said to one person informally
• не мочите = don’t get it wet, said politely or to more than one person

Yes, Russian word order is flexible, but the given order is very natural.

Standard version:

Не мочи телефон, иначе он перестанет работать.

You might also hear variations, but they can change emphasis. For example:

Иначе телефон перестанет работать, не мочи его.

This is possible, but much less neutral as a basic warning.

The original sentence sounds natural because it gives:

1. the instruction
2. then the consequence

That is a common pattern in Russian.

The stress is on the last syllable:

мочи́

A rough pronunciation guide:

• не = nye
• мочи́ = ma-CHEE
• телефон = tyel-ye-FON
• иначе = ee-NA-che
• он перестанет работать = on pye-rye-STAH-nyet ra-BO-tat

The important stress points are:

• мочи́
• телефо́н
• ина́че
• переста́нет
• рабо́тать

Yes, it is a common verb, but learners should be careful because it can have different meanings depending on context.

In ordinary everyday speech it can mean:

• to wet
• to soak
• to make something wet

But in slang or figurative contexts, it can have very different meanings, including very rough or violent ones. In this sentence, though, the meaning is completely harmless and practical: to get wet.

Because the object is телефон, the meaning is unmistakably:

Don’t get the phone wet.