الزبون الذي كان هناك في البنك نسي البطاقة.

Arabic can begin either with a noun or with a verb.

Here, الزبون الذي كان هناك في البنك is the topic, and then نسي البطاقة tells you what happened to him. So the sentence is structured a bit like:

• The customer who was there in the bank — forgot the card

This is completely natural in Arabic.

You could also make a more verb-first version, such as نسي الزبون..., but the original sentence puts focus first on the customer.

الذي is the relative pronoun, meaning who, that, or which depending on context.

So:

• الزبون الذي... = the customer who...

In this sentence, الذي كان هناك في البنك is a relative clause describing الزبون.

Because الزبون is:

• singular
• masculine
• definite

So the matching relative pronoun is الذي.

Some common forms are:

• الذي = singular masculine
• التي = singular feminine
• الذين = masculine plural
• اللاتي / اللواتي etc. = feminine plural

If the noun were feminine, for example الزبونة, you would use التي.

Because the sentence is talking about the customer, not just a customer.

So:

• زبون = a customer
• الزبون = the customer

Also, since the noun is definite, the relative clause uses the definite relative pronoun الذي. In other words, الذي normally follows a definite noun.

كان means was.

So:

• الذي كان هناك = who was there

Arabic often omits the verb to be in the present tense, but not in the past tense.

Compare:

• هو هناك = he is there
• هو كان هناك = he was there

Since this sentence refers to a past state, كان is needed.

هناك means there.

So:

• كان هناك = was there

It tells you the location in a general way, and then في البنك gives the specific place:

• هناك في البنك = there in the bank

It is a very natural combination in Arabic.

Yes, both relate to location, but they do slightly different things.

• هناك = there
• في البنك = in the bank

Together they give a fuller expression:

• كان هناك في البنك = was there in the bank

In English, this can sound a bit repetitive in some contexts, but in Arabic it is normal to combine a general location word like هناك with a more specific phrase like في البنك.

البنك is definite, so it means the bank.

• في بنك = in a bank
• في البنك = in the bank

The sentence is talking about a specific bank, or at least treats it as known in context.

نسي is a past-tense verb meaning forgot.

Its base verb is:

• نَسِيَ = to forget

In this sentence, نسي is:

• third person
• masculine
• singular
• past tense

So it means:

• he forgot

The subject is الزبون.

Because Arabic verbs already contain person, number, and gender information.

So نسي already tells you:

• he
• singular
• masculine
• in the past

Since the subject الزبون is already present, Arabic does not need an extra separate pronoun like هو.

Because it means the card, not a card.

So:

• بطاقة = a card
• البطاقة = the card

This usually suggests a specific card known from context, such as the customer’s bank card, ID card, or some previously understood card.

Arabic does not always need to say his if the context already makes it clear.

So نسي البطاقة can naturally mean:

• he forgot the card

And in context, that is often understood as his card.

If you wanted to make it explicit, you could say:

• نسي بطاقته = he forgot his card

But the original sentence is still perfectly normal.

Yes, in fully vocalized formal Arabic there are case endings, although they are often not written in everyday texts.

A fully vocalized version would be approximately:

• الزَّبونُ الَّذي كانَ هُناكَ في البنكِ نَسِيَ البِطاقةَ

The main endings are:

• الزبونُ = nominative, because it is the main subject
• البنكِ = genitive, because it comes after في
• البطاقةَ = accusative, because it is the direct object of نسي

In normal unvoweled writing, these endings usually do not appear.

Although it is written الزبون, it is pronounced with assimilation because ز is a sun letter.

So it is pronounced roughly:

• az-zabūn

not:

• al-zabūn

This happens because the ل of الـ assimilates to the following sun letter.

Yes, Arabic allows some flexibility in word order.

For example, you may also see structures like:

• الزبون الذي كان في البنك هناك نسي البطاقة
• نسي الزبون الذي كان هناك في البنك البطاقة

These can all be grammatical, but the original sentence is a very natural way to present the information. It first identifies the customer, then tells what he did.