אפשר לקבל כיסא נוסף ליד החלון?

In this sentence, אפשר means something like is it possible or can I / can we.

So אפשר לקבל כיסא נוסף ליד החלון? is literally closer to:

Is it possible to get an additional chair by the window?

This is a very common Hebrew way to make a polite request. Hebrew often uses אפשר + infinitive where English might use can I... or could we...

Examples:

• אפשר לשבת כאן? = Can I sit here?
• אפשר לשלם באשראי? = Can I pay by card?

Because Hebrew often leaves the subject unstated in polite requests when אפשר is used.

Instead of saying:

• אני יכול/ה לקבל כיסא נוסף? = Can I get another chair?

Hebrew very naturally says:

• אפשר לקבל כיסא נוסף?

This sounds less personal and often more polite or neutral, similar to English Could I get... or Would it be possible to get...

Also, אני יכול and אני יכולה would force you to choose masculine or feminine. אפשר לקבל... avoids that entirely and works for everyone.

Because after אפשר, Hebrew commonly uses an infinitive.

• אפשר = is it possible / can one
• לקבל = to receive / to get

So the structure is:

אפשר + infinitive

Examples:

• אפשר להיכנס? = May I come in?
• אפשר לראות את התפריט? = Can I see the menu?
• אפשר לקבל מים? = Can I get water?

So אפשר לקבל... literally means Is it possible to get...

Because in Hebrew, adjectives usually come after the noun.

• כיסא = chair
• נוסף = additional / extra

So:

• כיסא נוסף = an additional chair

This is the normal Hebrew word order.

More examples:

• בית גדול = a big house
• שולחן קטן = a small table
• כיסא נוח = a comfortable chair

English usually puts adjectives before the noun, but Hebrew usually puts them after.

נוסף means additional, extra, or another one added.

So כיסא נוסף means:

• an additional chair
• an extra chair

It is similar to אחר in some situations, but not exactly the same.

• כיסא אחר = a different chair / another chair
• כיסא נוסף = an extra chair / one more chair

So in a restaurant, if you need one more seat at the table, כיסא נוסף is the better choice.

Because את is used before a definite direct object, and כיסא נוסף here is indefinite.

Compare:

• אפשר לקבל כיסא נוסף? = Can I get an additional chair?
  No את, because it is a chair, not the chair.

But:

• אפשר לקבל את הכיסא הנוסף? = Can I get the additional chair?
  Here את appears because הכיסא הנוסף is definite: the additional chair.

This is a very important Hebrew grammar point:

• definite object → usually needs את
• indefinite object → no את

ליד החלון means next to the window or by the window.

The word החלון has ה־, the definite article, so it means the window.

In many real-life situations, especially in a restaurant, this sounds natural because the speaker means a specific location: by the window.

If you said ליד חלון, that would mean next to a window, which is less specific and often less natural in this kind of context.

So:

• ליד החלון = by the window
• ליד חלון = by a window

A natural pronunciation is:

Efshár lekabél kisé nosáf leyád hachalón?

Rough breakdown:

• אפשר = ef-SHAR
• לקבל = le-ka-BEL
• כיסא = ki-SE
• נוסף = no-SAF
• ליד = le-YAD
• החלון = ha-kha-LON

A few notes:

• The ח in החלון is a throat sound, like the ch in German Bach or Scottish loch.
• Stress is usually near the end in these words: efSHAR, lekaBEL, nosaF, hachalon.
• In everyday speech, כיסא is often pronounced ki-SE.

Yes, it is polite and natural.

אפשר לקבל כיסא נוסף ליד החלון? sounds perfectly normal in a service situation.

If you want to make it even softer or more explicitly polite, you can add בבקשה:

• אפשר לקבל כיסא נוסף ליד החלון, בבקשה?
  = Could I get an extra chair by the window, please?

Hebrew often relies on tone as well as wording. Even without בבקשה, this sentence is already polite.

No. That is one useful thing about this structure.

Because it uses אפשר + infinitive, the sentence does not show whether the speaker is male or female.

That makes it very convenient:

• men can say it
• women can say it
• groups can say it

If you used אני יכול or אני יכולה, then you would have to choose gender:

• אני יכול לקבל... = masculine speaker
• אני יכולה לקבל... = feminine speaker

But אפשר לקבל... works for everyone.

Hebrew often forms questions without changing word order. Intonation and context do a lot of the work.

So:

• אפשר לקבל כיסא נוסף ליד החלון. could be a statement depending on tone
• אפשר לקבל כיסא נוסף ליד החלון? is clearly a question

This is different from English, where word order often changes:

• You can get...
• Can you get...?

In Hebrew, the same basic order often stays the same, and the rising question intonation makes it a request or question.

Yes. In everyday spoken Hebrew, people often shorten requests.

For example:

• אפשר כיסא נוסף ליד החלון?
• יש כיסא נוסף ליד החלון? = Is there an extra chair by the window?
• אפשר עוד כיסא ליד החלון? = Can I get one more chair by the window?

Your original sentence is a full, clear, and polite version. Shorter versions may sound a bit more casual, but they are very common in speech.