Não deites fora o papel, por favor.

Deites comes from the verb deitar.

In this sentence, it is part of deitar fora, which means to throw away. So deites is the verb form being used for you in this command.

The dictionary form you would look up is deitar.

Because Portuguese uses the present subjunctive for negative commands.

So:

• positive command to tu: Deita fora o papel.
• negative command to tu: Não deites fora o papel.

This is a very common pattern in Portuguese:

• Fala → Não fales
• Come → Não comas
• Abre → Não abras

So não deites is exactly what you should expect for don’t throw away when speaking to tu.

Yes. Deitar fora is a very common verbal expression meaning to throw away or to discard.

Even though it is written as two words, learners should treat it as one unit of meaning:

• deitar fora o papel = to throw away the paper
• deitar fora o lixo = to throw away the rubbish
• deitar fora isso = to throw that away

So fora is not there by itself with a separate meaning in this sentence; it belongs with deitar.

Because in the expression deitar fora, the normal order is verb + fora.

So:

• deitar fora
• não deites fora o papel

This expression can also allow the object in between:

• Não deites o papel fora.

That is also natural. Both versions are used. The version in your sentence keeps deites fora together, which is very common.

Portuguese uses articles more often than English.

Here, o papel means the paper, and it usually refers to a specific piece of paper that both speaker and listener can identify from the context.

In English, we might sometimes just say Don’t throw away paper, but in Portuguese that would usually sound too general or unnatural in this situation. If you mean a particular paper, o papel is the normal choice.

It is informal singular, because deites is the form used with tu.

If you wanted a more formal singular version, you would normally say:

• Não deite fora o papel, por favor.

If you were speaking to more than one person:

• Não deitem fora o papel, por favor.

So the original sentence is what you would say to one person you address as tu.

Yes. That is also correct.

Both of these are possible:

• Não deites fora o papel.
• Não deites o papel fora.

They mean the same thing. Learners will hear both patterns. The version with fora right after the verb is very common and keeps the expression deitar fora together more clearly.

Por favor means please and makes the command more polite.

It does not have to be at the end. You can also say:

• Por favor, não deites fora o papel.
• Não deites fora o papel, por favor.

Both are correct. Putting it at the end is very natural and common.

A rough English-style guide is:

• Não ≈ now said through the nose
• deites ≈ DAY-tesh
• fora ≈ FO-ra
• o papel ≈ u pa-PELL
• por favor ≈ pur fuh-VOR

A few useful pronunciation notes for Portugal:

• não has a nasal sound
• final -s in deites sounds like sh
• r in fora is usually a light tap

So the whole sentence sounds roughly like:

nowng DAY-tesh FO-ra u pa-PELL, pur fuh-VOR

That is only an approximation, but it points you in the right direction.

In this sentence, it most naturally means a specific paper / the paper.

Because the sentence uses o papel, the speaker is probably talking about a particular item already visible or already mentioned.

If you were talking about paper as a material in a more general sense, the phrasing would usually be different. Here, the most natural reading is: don’t throw away that paper / the paper.