ماكينة الخياطة جاهزة، والخيط قربها.

Because Arabic often uses a nominal sentence in the present tense. In other words, Arabic can say:

ماكينة الخياطة جاهزة

without any separate word for is.

So the structure is simply:

• ماكينة الخياطة = the subject
• جاهزة = the predicate/descriptive part

This is the normal way to say The sewing machine is ready in the present.
If you wanted the past or future, then Arabic would usually add a verb, such as كانت for was.

Because it describes ماكينة, and ماكينة is feminine.

A very common sign of feminine nouns in Arabic is ـة / ة at the end, and ماكينة has that pattern. So the adjective must match it:

• masculine: جاهز
• feminine: جاهزة

This kind of agreement is very important in Arabic: adjectives normally match the noun in gender and number.

This is an iḍāfa construction, often called a genitive construction or noun-of-noun structure.

Literally, it is something like:

• ماكينة = machine
• الخياطة = the sewing

Together:

• ماكينة الخياطة = the machine of sewing = the sewing machine

This is a very common way Arabic makes compound nouns.

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

So Arabic says:

• ماكينة الخياطة

not:

• الماكينة الخياطة ✗

Even though ماكينة itself has no الـ, the whole phrase becomes definite because the second noun is definite: الخياطة.

So ماكينة الخياطة is understood as the sewing machine, not just a sewing machine of sewing.

قربها is made of two parts:

• قرب = near / nearby / vicinity
• ها = her / it (feminine singular)

So قربها means near it or by it, referring to a feminine noun.

In this sentence, it means the thread is located near the sewing machine.

It refers back to ماكينة الخياطة.

Since ماكينة is feminine, Arabic uses the feminine singular pronoun suffix ـها:

• ـه = him / it (masculine)
• ـها = her / it (feminine)

So قربها means near her/it, and here it means the sewing machine.

Because قرب here is not being used as an adjective. It is functioning more like near / nearby as an adverbial expression or noun of place.

So:

• الخيط قربها = the thread is near it

But Arabic can also express this idea with an adjective:

• الخيط قريب منها

That also means the thread is near it.

The two structures are similar in meaning, but the grammar is different:

• قربها = near it / in its vicinity
• قريب منها = close to it

If you used قريب, then it would agree with الخيط, which is masculine singular.

و simply means and.

It connects the two clauses:

• ماكينة الخياطة جاهزة
• الخيط قربها

So the sentence is made of two coordinated parts. This is very common in Arabic, just as in English.

Because it is a definite noun: the thread.

So in the second clause:

• الخيط = the thread
• قربها = near it

Arabic is saying the thread specifically, not just a thread.

Yes.

الخيط قربها is another nominal sentence:

• الخيط = subject
• قربها = predicate / locative expression

So both halves of the full sentence are nominal sentences joined by و.

A careful fully vowelled version would be:

مَاكِينَةُ الخِيَاطَةِ جَاهِزَةٌ، وَالخَيْطُ قُرْبَهَا.

A rough transliteration:

mākīnatu l-khiyāṭati jāhizatun, wal-khayṭu qurbahā

A few useful notes:

• ماكينةُ ends in ـُ because it is the subject of the first clause.
• الخياطةِ ends in ـِ because it is the second term of the iḍāfa.
• جاهزةٌ is the predicate of the first clause.
• الخيطُ is the subject of the second clause.

In everyday reading and speaking, those final case endings are often not pronounced fully, but they are part of formal grammar.

In both words, the ل of الـ is pronounced clearly:

• الخياطة = al-khiyāṭa
• الخيط = al-khayṭ

That is because خ is a moon letter, not a sun letter.

So unlike words such as الشمس, where the ل sound disappears in pronunciation, here it stays:

• الخياطة → the l is heard
• الخيط → the l is heard

Yes. A common alternative would be:

ماكينة الخياطة جاهزة، والخيط قريب منها.

That uses قريب من instead of قرب.

Both are natural, but they feel slightly different in structure:

• قربها = near it / by it
• قريب منها = close to it

A learner should recognize both patterns, because both are common in Modern Standard Arabic.