Learn Hardcore Turkish: Lütfen peyniri rendele.

Because -i is the accusative case marking a definite direct object. Peyniri means the cheese (a specific, known cheese). If you say peynir, it’s indefinite: cheese / some cheese.

Definite: Peyniri rendele. = Grate the cheese.
Indefinite: Peynir rendele. or Biraz peynir rendele. = Grate some cheese.

The vowel in the accusative suffix follows vowel harmony:

Last vowel a/ı → -ı (e.g., yağı “the oil”)
e/i → -i (e.g., peyniri “the cheese”)
o/u → -u (e.g., tuzu “the salt”)
ö/ü → -ü (e.g., sütü “the milk”)

What verb form is rendele?

It’s the second-person singular imperative of rendelemek (to grate). Imperatives tell someone to do something:

2nd sg (informal): rendele
2nd pl / polite singular: rendeleyin
Very formal/polite: rendeleyiniz

Is Lütfen peyniri rendele polite enough?

It’s softened by lütfen, but it’s still a direct command to someone you address as sen (informal). To be more polite/formal:

Polite request: Lütfen peyniri rendeleyebilir misiniz?
Neutral polite (no “please”): Peyniri rendeleyebilir misiniz?
Polite imperative: Lütfen peyniri rendeleyin.

How do I say “Please don’t grate the cheese”?

Use the negative imperative:

Informal: Lütfen peyniri rendeleme.
Polite/plural: Lütfen peyniri rendelemeyin.
Very formal: Lütfen peyniri rendelemeyiniz.

Why isn’t there a subject like sen?

Turkish imperatives normally omit the subject; sen is understood. You add sen or siz only for emphasis or contrast:

Sen peyniri rendele (You, grate the cheese) contrasts with someone else.
Siz peyniri rendeleyin is polite/plural and can also emphasize who should do it.

Can I move the words around?

Yes, Turkish word order is flexible, though the neutral order is object before the verb. All of these are possible, with slight shifts in emphasis:

Lütfen peyniri rendele. (neutral)
Peyniri lütfen rendele. (politeness sits next to the object)
Peyniri rendele lütfen. (please at the end; softer tone)
Lütfen rendele peyniri. (puts focus on the object at the end)
Rendele peyniri lütfen. (verb-first, stronger directive; emphasis on the object)

Placing an element at the end tends to emphasize it.

Can I replace peyniri with a pronoun?

Yes, if the context is clear:

Lütfen onu rendele. = Please grate it.
If you’re pointing: Lütfen bunu rendele. = Please grate this (one). Don’t keep both (onu peyniri)—just use one object.

How do I say “Grate some cheese,” not “the cheese”?

Use an indefinite object:

Peynir rendele.
Biraz peynir rendele.
Azıcık/birazcık peynir rendele. (colloquial “a little bit”)

What’s a more indirect/polite way to ask?

Requests with -ebilir + question particle are very natural:

Informal: Peyniri rendeleyebilir misin?
Polite/plural: Peyniri rendeleyebilir misiniz? You can add lütfen: Lütfen peyniri rendeleyebilir misiniz?

What’s the difference between rendelemek and rendelenmek?

rendelemek: to grate (active). Example: Peyniri rendele.
rendelenmek: to be grated (passive). Examples:
- Peynir rendelenir. = The cheese is (gets) grated. (used in recipes)
- Peynir rendelendi. = The cheese was grated.

Pronunciation tips for the sentence?

lütfen: ü is a front rounded vowel (like French “u” in “lune”). Try saying “ee” while rounding your lips.
peyniri: the ey sounds like “ay” in “day”; the final i is a clear “ee.”
rendele: stress typically falls near the end: ren-de-LE.
Turkish r is a quick tap, not the English approximant. Saying it smoothly: “LÜT-fen PEY-ni-ri ren-de-LE.”

What does -sene/-senize do, as in Peyniri rendelesene?

-sene/-senize softens a request in a friendly, coaxing way (often among friends/family):

Informal: Peyniri rendelesene. (Come on, grate the cheese.)
Polite/plural: Peyniri rendelesenize.

Could I specify the type of cheese instead of just peynir?

Yes. Commonly:

Kaşarı rendele. = Grate the kashar cheese.
Parmesanı rendele.
Beyaz peyniri rendele. Mark with accusative if definite: kaşarı / parmesanı / beyaz peyniri.