السترة خلف الباب.

In Arabic, simple present-tense sentences often have no written or spoken verb for is/are.

So:

السترة خلف الباب
literally looks like the jacket behind the door,
but it means The jacket is behind the door.

If you wanted a different tense, then Arabic would normally use a verb, for example:

• كانت السترة خلف الباب = The jacket was behind the door.
• ستكون السترة خلف الباب = The jacket will be behind the door.

This is a nominal sentence in Arabic, called جملة اسمية.

Its main parts are:

• السترة = the topic/subject (مبتدأ)
• خلف الباب = the predicate/comment (خبر)

More specifically, خلف الباب is a prepositional/adverbial-type phrase functioning as the predicate.

So the structure is:

[the jacket] [behind the door]

which Arabic uses to mean The jacket is behind the door.

This is a very common issue in Arabic. Normal Arabic writing usually leaves out short vowels, so learners must get them from:

• vocabulary study
• dictionaries
• context
• fully vowelled texts for beginners

In a fully vowelled version, this sentence is:

السُّتْرَةُ خَلْفَ الْبَابِ

So السترة here is pronounced approximately as-sutra in pause, or as-sutratu if full case endings are pronounced.

The important point is that the spelling السترة by itself does not show all the vowels.

Because س is a sun letter.

The Arabic definite article is written الـ, but its pronunciation changes with some letters:

• before a sun letter, the l sound assimilates
• before a moon letter, the l sound stays

So:

• السترة is written with ال
• but pronounced as-sutra, not al-sutra

By contrast:

• الباب has ب, which is a moon letter
• so it is pronounced al-bāb

The final ة is called tāʾ marbūṭa.

It often marks a noun as feminine, and سترة is grammatically feminine.

Its pronunciation changes slightly depending on context:

• in pause: usually -a or -ah
• with full grammatical endings: it is pronounced with a t sound before the ending

So you may hear or learn it as:

• sutra in pause
• sutratu / sutrata / sutrati in fully pronounced formal grammar

Because the noun is feminine, words that agree with it would usually also be feminine.

For a beginner, it is fine to think of خلف as meaning behind.

More precisely, in traditional Arabic grammar it is often treated as a noun of place / ظرف مكان rather than a simple preposition.

That matters because:

• خلف itself can take a case ending
• the noun after it is put in the genitive

So in full form:

خلفَ البابِ

This behaves a lot like behind the door in English, even though the internal grammar is a bit different.

Because it comes after خلف in the phrase خلف الباب.

In full grammatical form:

• خلفَ takes the accusative as a locative expression
• البابِ is genitive

So the fully vowelled phrase is:

خلفَ البابِ

Also, الباب has الـ because it means the door, not just a door.

In fully vowelled, careful MSA, the sentence is:

السُّتْرَةُ خَلْفَ الْبَابِ

The endings are:

• السُّتْرَةُ = nominative, because it is the مبتدأ
• خَلْفَ = accusative, because it is a locative adverb/noun of place
• الْبَابِ = genitive, because it is linked to خلف

In normal pause, many speakers and readers do not pronounce these final case vowels clearly, so you will often hear something closer to:

as-sutra khalf al-bāb

Yes, but changing the word order can change the feel or emphasis.

The basic sentence:

السترة خلف الباب
means The jacket is behind the door.

A different order such as:

خلف الباب سترةٌ
more naturally means There is a jacket behind the door or A jacket is behind the door.

That is because Arabic often prefers indefinite nouns like سترةٌ to come later rather than begin a neutral sentence.

So for a beginner:

• السترة خلف الباب = the jacket is behind the door
• خلف الباب سترةٌ = there is a jacket behind the door

No, but definiteness changes the meaning.

In your sentence:

• السترة = the jacket
• الباب = the door

So the sentence refers to specific things already known from context.

If you want a jacket instead, Arabic often prefers something like:

خلف الباب سترةٌ
= There is a jacket behind the door

Starting directly with an indefinite noun, as in سترةٌ خلف الباب, is possible in some contexts, but it is less neutral and less beginner-friendly as a default pattern.