الزجاج الأمامي نظيف.

Because Arabic usually leaves out the present-tense verb to be.

So الزجاج الأمامي نظيف is a complete sentence meaning The windshield is clean without any separate word for is.

This is called a nominal sentence. Its two main parts are:

• الزجاج الأمامي = the subject/topic
• نظيف = the predicate/comment

If you want was or will be, Arabic does use a verb, for example:

• كان الزجاج الأمامي نظيفًا = The windshield was clean.
• سيكون الزجاج الأمامي نظيفًا = The windshield will be clean.

Because in Arabic, an adjective normally comes after the noun it describes.

So:

• الزجاج الأمامي = literally the glass front in Arabic word order, but naturally the front glass / windshield

This is the normal pattern:

• noun + adjective

Examples:

• بيت كبير = a big house
• السيارة الجديدة = the new car
• الزجاج الأمامي = the front glass / windshield

It is not an iḍāfa here. الأمامي is an adjective meaning front or frontal.

So الزجاج الأمامي is:

• noun: الزجاج
• adjective: الأمامي

One clue is that الأمامي has الـ. In an adjective phrase, the adjective matches the noun in definiteness. That is exactly what happens here.

Also, because it is an adjective, it can change form:

• النافذة الأمامية = the front window

If it were a noun in iḍāfa, the structure would behave differently.

Because when an adjective describes a definite noun, the adjective must also be definite.

Here:

• الزجاج = the glass
• الأمامي = the front

So together:

• الزجاج الأمامي = the front glass / the windshield

This is called agreement in definiteness.

Compare:

• زجاج أمامي = front glass / a windshield
• الزجاج الأمامي = the front glass / the windshield

Because نظيف here is the predicate of the sentence, not an adjective inside the noun phrase.

So:

• الزجاج الأمامي نظيف = The windshield is clean.

In this kind of sentence, the predicate is usually indefinite, so نظيف does not take الـ.

If you say:

• الزجاج الأمامي النظيف

that means the clean windshield — just a noun phrase, not a complete sentence by itself.

So the difference is:

• الزجاج الأمامي نظيف = The windshield is clean.
• الزجاج الأمامي النظيف = the clean windshield

Because it matches الزجاج الأمامي, which is treated here as masculine singular.

Arabic adjectives agree with the noun they describe or refer back to in:

• gender
• number

So here the predicate is:

• نظيف = masculine singular clean

If the noun were feminine, you would usually use:

• نظيفة

For example:

• النافذة الأمامية نظيفة = The front window is clean.

So نظيف is used because the thing being talked about here is grammatically masculine singular.

Literally, it means the front glass.

In normal usage, though, it refers to the windshield or front windshield of a vehicle.

So Arabic often uses a descriptive phrase where English uses a single common word.

You can think of it as:

• زجاج = glass
• أمامي = front/front-facing

Together: front glass, meaning windshield.

A helpful pronunciation is:

az-zujāj al-ʾamāmī naẓīf

A few useful notes:

• الزجاج begins with ز, which is a sun letter, so الـ is assimilated in pronunciation:
  • written: الزجاج
  • pronounced: az-zujāj
• الأمامي begins with a hamza, so الـ is pronounced normally:
  • al-ʾamāmī
• نظيف is pronounced roughly:
  • naẓīf

So the whole sentence sounds like:

az-zujāj al-ʾamāmī naẓīf

The fully vowelled MSA form is:

الزُّجاجُ الأَمامِيُّ نَظيفٌ

These endings show grammatical case:

• الزجاجُ = nominative, because it is the subject of the nominal sentence
• الأماميُّ = nominative too, because it is an adjective matching الزجاج
• نظيفٌ = nominative, because it is the predicate

In careful formal reading, those endings matter. In pause, and in much real-life pronunciation, the final short vowels are often not clearly pronounced, so you often hear something closer to:

الزجاج الأمامي نظيف

In MSA, a common way is to use ليس:

الزجاج الأمامي ليس نظيفًا
= The windshield is not clean.

Notice that after ليس, the predicate is usually in the accusative, so:

• نظيف becomes نظيفًا

So:

• الزجاج الأمامي نظيف = The windshield is clean.
• الزجاج الأمامي ليس نظيفًا = The windshield is not clean.