رمل القطط نظيف.

This is an iḍāfa construction, often called a genitive construction or X of Y structure.

• رمل = sand
• القطط = the cats

So literally, رمل القطط means the sand of the cats. In natural English, that becomes cat litter or cats’ litter.

Arabic often expresses this kind of relationship by putting two nouns next to each other:

• first noun = the thing being possessed or described
• second noun = the owner/category

So رمل القطط is not a full sentence by itself; it is a noun phrase meaning cat litter.

In Arabic, the verb to be in the present tense is usually not written or spoken in simple sentences like this.

So:

• رمل القطط نظيف
• literally: cat litter clean
• natural English: The cat litter is clean

This is completely normal in Arabic. The present-tense is/are/am is understood automatically.

This sentence follows a very common Arabic pattern:

• subject/topic
  • description
• رمل القطط = the cat litter
• نظيف = clean

So the structure is:

• رمل القطط = the thing being talked about
• نظيف = what is being said about it

This is called a nominal sentence in Arabic. The adjective or descriptive word often comes after the noun it describes in this kind of sentence.

Because it agrees with رمل, which is:

• singular
• masculine

Even though القطط is plural, the main noun in the phrase is رمل. The sentence is about the litter/sand, not about the cats.

So:

• رمل → singular masculine
• therefore نظيف → singular masculine

If the main noun were feminine, the adjective would usually be feminine too.

Good question. In an iḍāfa construction, definiteness works a little differently from English.

In رمل القطط:

• رمل does not take الـ
• القطط does take الـ

When the second noun in the iḍāfa is definite, the whole phrase becomes definite. So رمل القطط means the cats’ litter or simply cat litter, depending on context.

Arabic often uses definiteness in places where English sounds more general.

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

So you say:

• رمل القطط

not:

• الرمل القطط

That would be incorrect for this structure.

A useful rule:

• first noun in iḍāfa: no الـ
• second noun: can be definite or indefinite depending on meaning

القطط is the plural of قِطّ or قِطَّة depending on the wording and context used for cat.

Here it means the cats.

So:

• قطة = a female cat / a cat
• قط = cat
• القطط = the cats

In this sentence, it is part of the phrase رمل القطط, meaning cat litter.

A careful pronunciation is:

ramlu l-qiṭaṭi naẓīfun

In everyday reading without full case endings, many learners will simply say:

raml al-qiṭaṭ naẓīf

A few notes:

• رمل = raml
• القطط = al-qiṭaṭ
• نظيف = naẓīf

Also notice:

• ط is an emphatic t
• ظ is an emphatic sound, often difficult for English speakers

Because Arabic is often written without full short vowels and case endings in normal texts.

The fully vowelled version would be:

رَمْلُ الْقِطَطِ نَظِيفٌ

Here:

• رملُ is nominative because it is the subject/topic
• القططِ is genitive because it is the second part of an iḍāfa
• نظيفٌ is nominative because it is the predicate

But in most everyday Arabic writing, these endings are omitted, so you usually see:

رمل القطط نظيف

It is an adjective in form, but in this sentence it functions as the predicate of the sentence.

That means it is not simply part of the noun phrase رمل القطط. Instead, it tells us something about that noun phrase:

• رمل القطط = the cat litter
• نظيف = is clean

So in meaning, نظيف works like clean in The cat litter is clean.

Yes. In fully correct vocalized MSA, that would be normal:

• رملُ القططِ نظيفٌ

The final ـٌ on نظيفٌ is the nominative tanwīn.

However, in ordinary unvowelled writing, people usually just write:

• رمل القطط نظيف

So both are the same sentence; one is just more fully marked for grammar.

English often uses a noun before another noun:

• cat litter
• dog food
• school bus

Arabic usually handles this with iḍāfa:

• رمل القطط = litter of cats / cat litter

So instead of stacking nouns the English way, Arabic typically uses the X of Y relationship.

That is why understanding iḍāfa is so important for Arabic learners.

Yes. Grammatically, that is the literal meaning.

• رمل = sand
• القطط = the cats
• نظيف = clean

So word-for-word, it is The cats’ sand is clean.

But depending on context, the natural meaning is usually The cat litter is clean. Arabic often uses ordinary literal wording for things that English expresses with a special compound noun.