Załóż ciepły sweter, bo jest zimno.

Załóż is the imperative singular form of założyć, meaning put on.

So this sentence is giving one person a command or suggestion:

• Załóż... = Put on...

It is addressed to you in the singular informal sense:

• to one person: załóż
• to more than one person / formal you: załóżcie or proszę założyć depending on the situation

Also, założyć is a perfective verb, so it focuses on completing the action: put it on.

This is a very common question.

• założyć = to put on
• nosić = to wear (in general, habitually, repeatedly)

So:

• Załóż ciepły sweter. = Put on a warm sweater.
• On nosi ciepłe swetry zimą. = He wears warm sweaters in winter.

If you want to say someone is wearing something right now, Polish often uses:

• mieć na sobie = to have on / to be wearing

For example:

• Ma na sobie ciepły sweter. = He/She is wearing a warm sweater.

Because sweter is the direct object of załóż, and with a masculine inanimate noun in the singular, the accusative usually looks the same as the nominative.

So:

• nominative: ciepły sweter
• accusative: ciepły sweter

That is why after załóż you still get:

• Załóż ciepły sweter.

If the noun were masculine animate, the accusative would usually change:

• widzę dobrego psa = I see a good dog

But sweter is inanimate, so no change here.

Ciepły agrees with sweter in:

• gender: masculine
• number: singular
• case: accusative (which here looks like nominative)

Because sweter is masculine singular, the adjective must match it:

• ciepły sweter

If the noun changed, the adjective would change too:

• ciepła kurtka = warm jacket
• ciepłe buty = warm shoes

So the adjective form is determined by the noun it describes.

Because zimno here does not describe a noun. It describes the situation / weather / temperature in a general, impersonal way.

• jest zimno = it is cold

In Polish, expressions like this often use an impersonal adverb-like form:

• jest zimno = it is cold
• jest ciepło = it is warm
• jest gorąco = it is hot

By contrast, zimny is an adjective used to describe a noun:

• sweter jest zimny = the sweater is cold
• zimny wiatr = cold wind

So:

• jest zimno = the weather/temperature is cold
• jest zimny = something masculine is cold

Because Polish often uses impersonal constructions where English uses it.

English says:

• It is cold.

Polish says:

• Jest zimno.

There is no need for a subject like it. This is very normal in Polish for weather, time, and general conditions:

• Jest późno. = It is late.
• Było ciemno. = It was dark.
• Będzie gorąco. = It will be hot.

So the missing it is not really missing from a Polish point of view.

Bo means because.

So:

• Załóż ciepły sweter, bo jest zimno. = Put on a warm sweater, because it’s cold.

Yes, you can often use ponieważ instead:

• Załóż ciepły sweter, ponieważ jest zimno.

The difference is mainly style:

• bo = very common, everyday, conversational
• ponieważ = more formal or more written

In normal speech, bo is extremely common.

Because in Polish, bo introduces another clause, and it is normally preceded by a comma.

So:

• Załóż ciepły sweter, bo jest zimno.

This is standard Polish punctuation.

A good practical rule for learners is:

• before bo, usually put a comma

The sentence is split into:

• Załóż ciepły sweter
• bo jest zimno

Yes, Polish word order is fairly flexible, although some versions sound more natural than others.

The original:

• Załóż ciepły sweter, bo jest zimno.

You could also say:

• Bo jest zimno, załóż ciepły sweter.

That is grammatically possible, but it sounds a bit more marked because it puts emphasis on the reason first.

The most natural neutral order here is the original one:

• command first
• reason second

So learners should treat the original sentence as the safest everyday version.

Yes. Sweter is a masculine noun.

You can tell partly from its ending:

• it ends in a consonant, which is very often masculine in Polish

Because it is masculine, adjectives agreeing with it take masculine forms:

• ciepły sweter
• nowy sweter
• gruby sweter

And because it is masculine inanimate, the singular accusative is the same as the nominative:

• sweter → sweter

Learners often ask this because English uses put on very broadly.

The most standard verb here is:

• założyć sweter = to put on a sweater

You will also hear forms related to ubrać, but they work a bit differently:

• ubrać się = to get dressed
• ubrać kogoś = to dress someone

So for this exact sentence, załóż ciepły sweter is the clearest and most natural choice.

A useful contrast:

• Załóż sweter. = Put on a sweater.
• Ubierz się ciepło. = Dress warmly.

Załóż comes from the perfective verb założyć, which fits a single completed action:

• Put it on.

That is why it sounds natural in this context: someone should do one specific thing now.

Zakładaj would come from the imperfective verb zakładać. It can appear in some contexts, but it usually has a different feel, for example:

• repeated action
• process
• stronger insistence in some situations
• instructions while the action is happening

In a simple one-time command like this, załóż is the most natural choice.

A rough pronunciation guide:

• Załóż ≈ za-woosh

  • ł sounds like English w
  • ó sounds like oo
  • ż sounds like the s in measure

• ciepły ≈ CHYEH-pwy

  • cie sounds roughly like chye
  • ł again sounds like w

• sweter ≈ SVEH-ter

• bo ≈ boh

• jest ≈ yest

• zimno ≈ ZEEM-no

A very rough full version:

• za-WOOSH CHYEH-pwy SVEH-ter, boh yest ZEEM-no

Not perfect, but good enough as a starting point.

It can be understood as any of those depending on tone and context.

Grammatically, załóż is an imperative, so it is literally a command form. But in real use it can sound like:

• a direct command
• practical advice
• a caring suggestion

For example, a parent, friend, or partner might say it simply to be helpful:

• Załóż ciepły sweter, bo jest zimno.

So the grammar is imperative, but the tone does not have to be harsh.