القميص جاف.

Because Arabic usually does not use a separate present-tense verb for to be in simple sentences like this.

So:

• القميص جاف = The shirt is dry

This is called a nominal sentence in Arabic. It has:

• القميص = the subject/topic
• جاف = the predicate/comment

If you want past or future, then Arabic does use a verb:

• كان القميص جافًّا = The shirt was dry
• سيكون القميص جافًّا = The shirt will be dry

Yes. جاف means dry, and here it functions as the predicate adjective: it tells you a quality of the shirt.

So the structure is:

• القميص = the shirt
• جاف = dry

Together: The shirt is dry.

Because here جاف is not directly modifying the noun. It is the predicate of the sentence.

Compare these two:

• القميصُ جافٌّ = The shirt is dry
• القميصُ الجافُّ = the dry shirt

That is a very important difference:

• no ال on جاف → a full sentence
• ال on الجاف → a noun phrase, not a full sentence

In Arabic, adjectives normally come after the noun they relate to.

That is true both when the adjective is:

1. describing the noun directly

   • القميص الجاف = the dry shirt

2. serving as the predicate in a sentence

   • القميص جاف = the shirt is dry

So seeing the describing word after the noun is completely normal in Arabic.

The key clue is definiteness.

• القميص جاف → The shirt is dry

  • first word is definite
  • second word is indefinite
  • this gives you a sentence

• القميص الجاف → the dry shirt

  • both words are definite
  • this gives you a noun phrase

So Arabic uses definiteness to help show the difference between:

• a complete statement
• a noun + adjective phrase

A full vocalized version is:

• القَمِيصُ جَافٌّ

A common transliteration is:

• al-qamīṣu jāffun

If you pause at the end, as people usually do in normal speech, it is often pronounced more like:

• al-qamīṣ jāff

A few pronunciation notes:

• ق in القميص is q, a deep back-of-the-mouth sound
• ص is an emphatic s
• جافّ has a long ā
• the final فّ is doubled because of the shadda

In fully inflected MSA, the sentence is:

• القميصُ جافٌّ

Both parts are in the nominative because this is a basic nominal sentence:

• القميصُ = nominative subject/topic
• جافٌّ = nominative predicate

In most everyday printed Arabic, these short vowels are omitted, so you usually see:

• القميص جاف

That is completely normal.

Yes. Predicate adjectives in Arabic agree with the noun in gender and usually number.

Here:

• قميص is masculine singular
• so جاف is also masculine singular

For example, with a feminine noun:

• النافذة جافة = The window is dry

So the adjective changes to match the noun.

قميص is masculine in Modern Standard Arabic.

That is why the predicate is the masculine form:

• القميص جاف

If the noun were feminine, the adjective would usually take ـة:

• الورقة جافة = The paper is dry

It is a nominal sentence (جملة اسمية).

The two main parts are:

• المبتدأ = the thing being talked about
  here: القميص
• الخبر = what is said about it
  here: جاف

So grammatically, القميص جاف is a classic mubtadaʾ + khabar structure.

A common MSA way is:

• القميصُ ليس جافًّا

Here ليس means is not.

Notice that after ليس, the predicate is normally accusative:

• جافًّا

So:

• القميصُ جافٌّ = The shirt is dry
• القميصُ ليس جافًّا = The shirt is not dry

You can, but the meaning/context changes.

• القميص جاف = The shirt is dry
• قميصٌ جافٌّ = A shirt is dry or a dry shirt, depending on context and full sentence structure

For a simple, clear sentence meaning The shirt is dry, القميص جاف is the natural form.