السحاب قرب الدرز.

Because this is a nominal sentence in Arabic. In the present tense, Arabic usually does not use a separate word for is/are.

So Arabic can simply say:

• السحاب قرب الدرز
• literally: the cloud(s) near the seam

But in natural English, you add is/are when translating.

If you wanted was/were, Arabic would usually use كان or a related form.

Here قرب is best understood as a noun/adverb of place meaning near or in the vicinity of.

So the structure is:

• السحاب = the subject
• قرب الدرز = the predicate, meaning near the seam

A useful thing to know is that unvocalized Arabic can be ambiguous. The spelling قرب could represent different forms in other contexts, but here it is being used in the near sense, not as a past-tense verb.

Because قرب and قريب are two different patterns.

• قرب الدرز = near the seam
• قريب من الدرز = close to the seam

Both are possible in MSA, but the grammar is different:

• قرب is followed directly by a noun
• قريب is often followed by من

So this sentence is using the قرب + noun pattern.

A fully vowelled version would typically be:

السَّحابُ قُرْبَ الدَّرْزِ

Grammatically:

• السحابُ = nominative, because it is the subject
• قربَ = accusative, because it functions like an adverbial expression of place
• الدرزِ = genitive, because it comes after قرب in this construction

In normal Arabic writing, these short vowels are usually omitted.

In both words, the ل of ال is assimilated because the next letter is a sun letter.

• السحاب is pronounced roughly as-saḥāb
• الدرز is pronounced roughly ad-darz

So you do not say al-saḥāb or al-darz in careful MSA pronunciation.

The spelling stays ال, but the pronunciation changes.

السحاب is often treated as a collective noun in MSA. It refers to clouds/cloud mass rather than one clearly counted cloud.

That means:

• it can have a plural meaning
• but grammatically it is often treated like a singular masculine noun

Related forms:

• سحابة = one cloud
• سحب = clouds

So if the meaning shown to you was plural in English, that is not surprising.

Because both are definite.

• السحاب = the cloud(s)
• الدرز = the seam/stitch

So the sentence is talking about specific, known things, not just any cloud(s) or any seam.

If the nouns were indefinite, the meaning would be more like clouds near a seam or a cloud near a seam, depending on context.

Yes, it is grammatical and understandable in MSA.

That said, many learners will more often meet the pattern:

• السحاب قريب من الدرز

This is also a natural MSA way to express being near.

So:

• قرب الدرز is concise and perfectly correct
• قريب من الدرز may feel more familiar to beginners

Both are useful to recognize.