هذا مكتب خاص.

In careful Modern Standard Arabic, it is pronounced:

hādhā maktabun khāṣṣun

A few notes:

• هذا = hādhā = this
• مكتب = maktab
• خاص = khāṣṣ

Pronunciation tips:

• kh is like the sound in German Bach or Scottish loch
• ṣ is an emphatic s
• the doubled ṣṣ in خاصّ means that sound is held a little longer

In everyday speech or in unvocalized reading, learners often say it more simply as hādhā maktab khāṣṣ.

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

So:

• هذا مكتب خاص literally looks like this office private
• but the natural English meaning is This is a private office

This is a very common Arabic pattern, often called a nominal sentence.

If you wanted the past tense, Arabic would use a verb, for example:

• كان هذا مكتبًا خاصًّا = This was a private office

Because مكتب is a masculine singular noun.

In Arabic, the demonstrative must match the noun’s gender:

• هذا = this for masculine singular
• هذه = this for feminine singular

Since مكتب is masculine, you say:

• هذا مكتب خاص

If the noun were feminine, you would use هذه, for example:

• هذه غرفة خاصة = This is a private room

Here, مكتب most naturally means office.

However, مكتب can also mean things like:

• desk
• office
• bureau

The exact meaning depends on context. In this sentence, if the meaning shown to the learner is This is a private office, then office is the intended sense.

Because in Arabic, adjectives usually come after the noun they describe.

So:

• مكتب خاص = literally office private
• natural English = private office

This is the normal word order in Arabic:

• noun first
• adjective second

Because مكتب is indefinite here, and the adjective must match it.

So:

• مكتب خاص = a private office
• both words are indefinite

In Arabic, adjectives agree with the noun in:

• definiteness
• gender
• number
• case

Compare:

• مكتب خاص = a private office
• المكتب الخاص = the private office

So خاص does not take الـ here because مكتب also does not have الـ.

Normally, no. In standard Arabic, هذا مكتب خاص is understood as a full sentence:

This is a private office

If you want this private office as a noun phrase, you would usually say:

هذا المكتب الخاص

That is because the noun phrase with this is typically definite, and the noun and adjective take الـ.

So the contrast is:

• هذا مكتب خاص = This is a private office
• هذا المكتب الخاص = this private office or this is the private office, depending on context

Fully vocalized, it is:

هٰذا مَكْتَبٌ خاصٌّ

In transliteration: hādhā maktabun khāṣṣun

Why those endings?

• مكتبٌ has -un
• خاصٌّ also has -un

That is because both are in the nominative in this kind of sentence.

A simple way to think about it:

• هذا = the topic or subject-like part
• مكتبٌ خاصٌّ = the predicate

In normal everyday writing, these short vowel endings are usually not written, so you often just see:

هذا مكتب خاص

Not always. خاص can mean:

• private
• special
• particular
• personal in some contexts

Its exact meaning depends on the situation.

For example:

• مكتب خاص often means private office
• شيء خاص could mean something special or something private, depending on context

So in this sentence, private is a very natural translation, but the word itself is a little broader than that.