عندما كنت أنتظر دوري في البنك، كانت الموظفة تكتب على ورقة.

عندما means when in the sense of at the time that.

In this sentence, it introduces a time clause:

عندما كنت أنتظر دوري في البنك
= When I was waiting for my turn in the bank

It is commonly used to connect one action to another action happening at the same time or around the same time.

A useful point: عندما is often followed by a verbal sentence, and the clause after it gives the time background for the main event.

كنت أنتظر is a past continuous-style structure:
كنت + imperfect verb

So:

• كنت أنتظر = I was waiting
• انتظرت = I waited

In this sentence, the speaker is describing an ongoing background action in the past. That is why كنت أنتظر is used.

So the contrast is:

• كنت أنتظر دوري → I was in the middle of waiting
• انتظرت دوري → I waited for my turn / I did wait for my turn

The first one fits better because another action was happening during that time: the employee was writing.

This is very common in Arabic.

Arabic often expresses was doing by using:

• كان / كنت / كانت... in the past
• followed by an imperfect verb

So:

• كنت أنتظر = I was waiting
• كانت تكتب = she was writing

The imperfect here does not mean present time by itself. With كان, it often describes an ongoing or repeated action in the past.

دوري means my turn.

It comes from دور, which can mean turn, role, or cycle, depending on context.

Here:

• دور = turn
• دوري = my turn

The ـي at the end is the possessive suffix meaning my.

So:

• دورك = your turn
• دوره = his turn
• دورها = her turn
• دوري = my turn

في البنك means in the bank.

• في = in / at
• البنك = the bank

In English, we often say at the bank, but Arabic commonly uses في for locations where something is happening.

So في البنك is completely natural.

Because الموظفة is a feminine noun meaning the female employee.

Arabic verbs agree with the subject in gender. Since the subject is feminine singular, the verb is feminine singular too:

• كانت = she was
• تكتب = she writes / was writing in this context

So:

كانت الموظفة تكتب
= The employee was writing

If the subject were masculine, you would say:

كان الموظف يكتب
= The male employee was writing

Yes, the imperfect form تكتب can mean different things depending on context:

• you write (masculine singular)
• she writes

Here, the context makes it clear that it means she was writing, because it follows كانت الموظفة.

So in this sentence:

كانت الموظفة تكتب
the subject is clearly the female employee, so تكتب means she writes / was writing.

This is a normal feature of Arabic verb forms: one form can have more than one possible meaning until context clarifies it.

Arabic often allows both verb-first and subject-first word order.

Here we have:

كانت الموظفة تكتب

This is a very natural structure in Arabic:
verb + subject + rest of sentence

You could also sometimes see a more subject-first structure in Arabic, but the version in the sentence is standard and common.

For learners, it is useful to get comfortable with Arabic frequently putting the verb before the subject.

على ورقة means on a piece of paper or on paper.

• على = on
• ورقة = paper / sheet of paper / piece of paper

In Arabic, ورقة often refers to a sheet or piece of paper, not the general material paper in the abstract.

So:

كانت الموظفة تكتب على ورقة
= The employee was writing on a piece of paper

Because the sentence does not refer to a specific known sheet of paper.

• على ورقة = on a piece of paper / on some paper
• على الورقة = on the paper / on the specific paper

Using the indefinite noun here is natural because the exact paper is not important. The sentence just tells us that she was writing on some sheet of paper.

Because Arabic often shows possession by adding a suffix directly to the noun.

So instead of saying a separate word for my, Arabic attaches ـي:

• دور = turn
• دوري = my turn

This is different from English, where possession is usually shown by a separate word such as my, your, his, and so on.

This suffix system is extremely common in Arabic:

• كتابي = my book
• اسمي = my name
• بيتي = my house

Because both actions are being described as ongoing in the past.

The sentence has two past background actions:

• كنت أنتظر دوري = I was waiting for my turn
• كانت الموظفة تكتب = the employee was writing

This creates the sense that both actions were happening at the same time.

Arabic often uses كان + imperfect in this way to describe simultaneous ongoing past events.

The comma simply separates the time clause from the main clause:

• عندما كنت أنتظر دوري في البنك = time/background
• كانت الموظفة تكتب على ورقة = main statement

In Arabic writing, punctuation is used, though sometimes less rigidly than in English. The comma here helps readability and makes the sentence structure clearer.

It specifically means a female employee.

• موظف = male employee / employee
• موظفة = female employee

The ـة ending is a very common marker of feminine nouns in Arabic.

In English, we often just say the employee without marking gender, but Arabic makes the gender explicit here.

It would become:

عندما كنت أنتظر دوري في البنك، كان الموظف يكتب على ورقة.

Changes:

• كانت → كان
• الموظفة → الموظف
• تكتب → يكتب

That is because the subject is now masculine singular.

Yes, that is exactly how it is naturally understood.

The first clause sets the scene:

When I was waiting for my turn in the bank...

The second clause tells what was happening during that time:

...the employee was writing on a piece of paper.

So the sentence gives a past-time background situation, with two simultaneous ongoing actions.