Daj mi znać wieczorem.

Daj znać is a very common Polish expression meaning let me know, tell me, or keep me informed depending on context.

Literally, it comes from:

• daj = give
• znać = connected with knowing

So the literal idea is something like give knowledge / give a sign, but in real usage you should learn it as a fixed phrase: daj znać = let me know.

Daj is the imperative form of dać, meaning give.

Here it is used to tell one person informally to do something:

• daj = let me know / tell me

It is the form you use when speaking to:

• one friend
• one family member
• one child
• one person you know well

Related forms:

• dajcie znać = tell me / let me know, addressing more than one person
• proszę dać znać = please let me know, more polite/formal

Mi means to me.

In Daj mi znać, the structure is literally:

• daj = give
• mi = to me
• znać = notice/information/word in this fixed expression

So the sentence is built like give me word / let me know.

In natural English, we do not say it that way, but grammatically in Polish mi is the person receiving the information.

Mi is in the dative case.

The dative is often used for the person who receives something. Since dać means to give, Polish uses the dative for the recipient:

• daj mi = give to me
• daj mu = give to him
• daj jej = give to her

So in Daj mi znać, mi is dative because it means to me.

Both can mean me, but mi is the normal unstressed short form in sentences like this.

So:

• Daj mi znać = the most natural form

Mnie is used when:

• you want emphasis
• it comes after some prepositions
• the sentence structure requires the full form

For example:

• Daj znać mnie is not natural here
• Daj mnie znać is incorrect
• Mnie daj znać, nie jemu = Let me know, not him

So in this sentence, mi is the standard choice.

Because dać znać is a fixed verbal expression.

Polish often creates expressions with:

• a conjugated verb first
• then an infinitive

Here:

• daj is conjugated
• znać stays in the infinitive

You do not change znać to match the subject here. The main grammatical action is carried by dać.

Compare:

• Dam ci znać = I will let you know
• Dał mi znać = He let me know
• Daj mi znać = Let me know

In all of these, znać stays the same.

Wieczorem means in the evening or this evening, depending on context.

So:

• Daj mi znać wieczorem = Let me know in the evening / this evening

Polish often uses a single word for time expressions where English uses a preposition plus noun.

Other examples:

• rano = in the morning
• nocą = at night
• latem = in summer
• zimą = in winter

Because Polish often uses the instrumental case for certain time expressions.

The base noun is:

• wieczór = evening

But in the sentence it becomes:

• wieczorem = in the evening

This is a common pattern with parts of the day, seasons, and similar expressions. It functions adverbially, telling you when something happens.

You do not need to translate the case literally. It is best to learn wieczorem as the standard form meaning in the evening.

It is informal, because daj is the singular informal imperative.

You would use Daj mi znać wieczorem with:

• a friend
• a sibling
• a partner
• someone your age you speak to casually

More formal versions include:

• Proszę dać mi znać wieczorem.
• Niech mi pan da znać wieczorem.
• Niech mi pani da znać wieczorem.

These are better when speaking politely to someone you do not know well, an older person, or in professional situations.

Yes. Polish word order is more flexible than English, though the basic version here is very natural:

• Daj mi znać wieczorem.

You could also say:

• Wieczorem daj mi znać. = emphasis on in the evening
• Daj znać mi wieczorem. = grammatically possible in some contexts, but less natural than daj mi znać wieczorem

The most neutral and common order is:

• Daj mi znać wieczorem.

Because dać is perfective, and here the speaker wants one completed action: one message, one update, one act of letting someone know.

So:

• Daj mi znać wieczorem = let me know this evening, once

If you used the imperfective dawać, it would suggest repeated or ongoing action, which usually does not fit this situation.

Compare:

• Daj mi znać = let me know
• Dawaj mi znać = keep letting me know / keep me updated

So dać is the natural choice for a single request.

Yes, you can.

Daj znać wieczorem still means let me know this evening, and in many situations me is understood from context.

However:

• Daj mi znać wieczorem is a bit clearer and slightly fuller
• Daj znać wieczorem can sound a little more general or casual

Both are common and natural.