ينتظر الزبون خارج غرفة القياس.

A careful MSA pronunciation with full case endings is:

yantaẓiru z-zabūnu khārija ghurfati l-qiyāsi

A few helpful notes:

• ينتظر = yantaẓiru
• الزبون is pronounced az-zabūn in connected speech, because ز is a sun letter, so the l of ال is assimilated
• غرفة is pronounced ghurfat here, not ghurfah, because it is followed by another noun in an iḍāfa structure
• القياس = al-qiyās

In less formal everyday reading, people often drop the final short vowels.

ينتظر is the imperfect verb, 3rd person masculine singular.

So it means:

• he waits
• he is waiting

In this sentence, the subject is الزبون = the customer, so ينتظر الزبون means the customer waits / is waiting.

The dictionary form is انتظر = to wait.

Yes. It comes from the same root letters:

• ن ظ ر

But the meaning is different because the verb is in a different pattern.

• نَظَرَ usually means to look
• اِنْتَظَرَ means to wait

This is very common in Arabic: the same root can produce different meanings in different verb forms.

Because verb–subject order is very common in Modern Standard Arabic.

So:

• ينتظر الزبون خارج غرفة القياس
  = a normal VSO sentence

You can also say:

• الزبون ينتظر خارج غرفة القياس

That is also correct, but it gives the sentence a slightly different feel, with more focus on the customer as the topic.

Because ز is one of the sun letters.

When ال comes before a sun letter:

• the l sound is not pronounced
• the following consonant is doubled

So:

• الزبون is written with ال
• but pronounced az-zabūn

This is a pronunciation rule only. The spelling does not change.

Because غرفة القياس is an iḍāfa construction, often called a construct phrase.

Structure:

• غرفة = room
• القياس = the measuring / fitting

Together:

• غرفة القياس = the fitting room or literally the room of measuring/fitting

In an iḍāfa:

• the first noun usually does not take ال
• the whole phrase can still be definite if the second noun is definite

So غرفة القياس is definite even though غرفة has no ال.

Here خارج means outside or outside of.

Grammatically, it is often treated as a noun used adverbially or as a word of place. In practice, for a learner, the important point is:

• خارج + noun = outside (of) + noun

So:

• خارج غرفة القياس = outside the fitting room

Unlike English, Arabic does not need an extra word like of here.

Because of the way the phrase is built.

First:

• خارج is followed by a noun that depends on it
• so غرفة comes in the genitive

Then:

• غرفة القياس is an iḍāfa
• in an iḍāfa, the second noun is also genitive

So the full form is:

• خارجَ غُرفةِ القِياسِ

Both غرفة and القياس are genitive, but for different structural reasons inside the phrase.

With full case endings, the sentence is:

يَنتَظِرُ الزَّبُونُ خارِجَ غُرفَةِ القِياسِ

Here is why:

• يَنتَظِرُ: indicative imperfect verb, so it ends in -u
• الزَّبُونُ: subject, so it is nominative
• خارِجَ: adverbial expression of place, so it is commonly accusative
• غُرفَةِ: genitive after خارج
• القِياسِ: genitive as the second noun of the iḍāfa

In ordinary Arabic writing, these short vowels are usually not written.

It can mean either one, depending on context.

The Arabic imperfect often covers both:

• the customer waits
• the customer is waiting

In this sentence, English would often naturally use is waiting, especially if describing what is happening right now.

Literally, it means something like:

• the measuring room
• the fitting room

In real usage, it refers to the place where a customer tries on clothes, so the most natural English translation is usually:

• fitting room
• sometimes changing room, depending on context

So although قياس often relates to measuring, the whole phrase works idiomatically as a store-related expression.

Yes, absolutely.

Both are correct:

• ينتظر الزبون خارج غرفة القياس
• الزبون ينتظر خارج غرفة القياس

The difference is mainly one of style and emphasis:

• ينتظر الزبون... is a very normal formal Arabic sentence pattern
• الزبون ينتظر... puts more attention on the customer

So as a learner, you should understand and be comfortable with both.