Sahi, boş ver o kartı.

Boş ver is the 2nd person singular imperative form of boş vermek. In other words, it is a command addressed to you.

The full subject would be sen, but Turkish usually leaves subject pronouns out when they are obvious. So:

• (Sen) boş ver = You, forget it / let it go / ignore it

Even though vermek by itself means to give, the expression boş vermek is an idiom and should be learned as a whole.

Not really. Literally, the parts are boş = empty and ver = give, but the expression boş vermek does not mean something like give empty in normal usage.

As a fixed expression, it means things like:

• forget it
• never mind
• let it go
• ignore it

So it is best to treat boş vermek as a single idiomatic verb phrase.

In standard Turkish, it is normally written boş ver as two words, because it comes from the verb phrase boş vermek.

In very informal writing, especially texting, you may sometimes see boşver, but learners should generally write boş ver.

Because o kartı is a definite/specific direct object, and Turkish usually marks that with the accusative ending.

So:

• o kart = that card as a basic noun phrase
• o kartı = that card as the specific object of the verb

In this sentence, the speaker is talking about a particular card, so the accusative is natural.

The Turkish accusative suffix changes according to vowel harmony:

• -ı
• -i
• -u
• -ü

The last vowel in kart is a, which is a back unrounded vowel, so the correct accusative form is kartı.

Because kart ends in a consonant, the suffix is added directly:

• kart
  • -ı → kartı

Here o is a demonstrative, meaning that.

So o kartı means that card.

Turkish o can also mean he, she, or it in other contexts, but when it comes before a noun, as in o kartı, it means that.

Turkish word order is flexible, so several versions are possible.

• Boş ver o kartı
• O kartı boş ver

Both are natural. Starting with boş ver puts the command first and can sound a little more immediate. Starting with o kartı gives a bit more focus to that card.

So this is a matter of emphasis and style, not a different basic meaning.

Not necessarily. It is usually casual and colloquial. Depending on tone, it can sound:

• relaxed: never mind
• reassuring: let it go
• dismissive: forget it
• sharper: drop it

So the sentence itself is not automatically rude, but tone of voice and situation matter a lot.

Yes. The sentence Boş ver o kartı is complete on its own.

Adding sahi gives an extra conversational flavor, as if the speaker has just remembered something or is changing direction slightly in the conversation.

The command form itself already shows that the sentence is addressed to you singular. Turkish often leaves pronouns out when the verb form makes them clear.

So:

• Boş ver already means you forget it / you let it go

If you wanted a polite or plural form, you would use boş verin instead.

You would use the plural/polite imperative:

• Sahi, boş verin o kartı.

Here boş verin can mean either:

• you all, forget that card
• please forget that card when addressing one person politely

So -in marks the plural/polite command form.