مبلغ الضمان كبير.

Arabic often leaves out the present-tense is/are in simple statements.

So مبلغ الضمان كبير literally looks like the amount of the guarantee big, but it means The guarantee amount is large.

This is a nominal sentence in Arabic:

• مبلغ الضمان = the topic / subject
• كبير = the predicate / comment about it

If you wanted a past-tense version, you would normally add a verb such as كان:

• كان مبلغ الضمان كبيرًا = The guarantee amount was large

A fully vocalized version is:

مَبْلَغُ الضَّمَانِ كَبِيرٌ

A careful MSA pronunciation is:

mablaghu ḍ-ḍamāni kabīrun

In pause, the final case ending is often not pronounced, so you may hear:

mablaghu ḍ-ḍamāni kabīr

Two pronunciation notes:

• غ in مبلغ is the sound gh
• الضمان is pronounced aḍ-ḍamān, not al-ḍamān, because ض is a sun letter

It is an iḍāfa construction, often called a genitive construct or noun-noun phrase.

Structure:

• مبلغ = amount / sum
• الضمان = the guarantee / deposit

Together:

• مبلغ الضمان = the amount of the guarantee or the guarantee amount

In Arabic, iḍāfa is a very common way to express of:

• باب البيت = the door of the house
• اسم الطالب = the student’s name
• مبلغ الضمان = the amount of the guarantee

Because in an iḍāfa, the first noun normally does not take الـ.

So Arabic says:

• مبلغ الضمان

not:

• المبلغ الضمان

The whole phrase can still be definite even though the first noun has no الـ.
Here, because الضمان is definite, the whole phrase مبلغ الضمان is also definite.

This is a key rule:

• first noun in iḍāfa: no الـ
• definiteness usually comes from the second noun

For the same reason: it is the first term of an iḍāfa.

The first noun in an iḍāfa:

• does not take الـ
• does not take tanwīn

So you get:

• مبلغُ الضمانِ

not:

• مبلغٌ الضمانِ

That missing tanwīn is one of the signals that مبلغ is linked to the next noun in an iḍāfa.

Because it is the second noun in an iḍāfa.

In Arabic, the second part of an iḍāfa is called مضاف إليه, and it is put in the genitive case.

So:

• الضمانِ ends with a genitive vowel in full vocalization

Full parsing:

• مبلغُ = nominative
• الضمانِ = genitive
• كبيرٌ = nominative

Because here كبير is the predicate of the sentence, not part of the noun phrase.

So:

• مبلغ الضمان كبير = The guarantee amount is large

But compare:

• مبلغ الضمان الكبير = the large guarantee amount

In the second example, الكبير is an adjective modifying the noun phrase, so it is definite.

In your sentence, كبير is not modifying مبلغ الضمان inside the phrase; it is telling you something about it. That is why the plain predicate form كبير is used.

Syntactically, it is the predicate (خبر).

Semantically, it still has adjective-like meaning: big / large. But in this sentence it functions like is large in English.

So the sentence pattern is:

• مبلغ الضمان = subject/topic
• كبير = predicate

A useful contrast:

• مبلغ الضمان كبير = The guarantee amount is large
• مبلغ الضمان الكبير = the large guarantee amount

That difference is very important in Arabic.

Because it matches مبلغ, which is a masculine singular noun.

In Arabic, predicates and adjectives usually agree with the noun in gender and number.

So:

• مبلغ is masculine singular
• therefore كبير is masculine singular

If the main noun were feminine, you would expect كبيرة instead.

Because ض is a sun letter.

When الـ comes before a sun letter, the ل sound is not pronounced, and the next consonant is doubled.

So:

• written: الضمان
• pronounced: aḍ-ḍamān

You can see this in the shadda on ض in full vocalization:

• الضَّمَان

This happens with all sun letters, such as:

• الشمس → ash-shams
• الطالب → aṭ-ṭālib
• الضمان → aḍ-ḍamān

The normal, neutral order is:

مبلغ الضمان كبير

This is the best order for a learner to use.

Arabic can sometimes move elements for emphasis, especially in formal or literary styles, for example:

• كبيرٌ مبلغُ الضمانِ

That can sound more emphatic, like Large is the guarantee amount or The guarantee amount is indeed large, but it is not the basic beginner pattern.

So as a rule:

• use مبلغ الضمان كبير
• recognize other orders later as stylistic or emphatic variations