هو يستبدل البرغي بقطعة الغيار.

يستبدل means he replaces, he substitutes, or he exchanges depending on context.

It is a Form X verb:

• past: استبدل = he replaced
• present: يستبدل = he replaces / he is replacing

Its root is ب د ل, which has to do with changing or substituting.

So in this sentence, يستبدل is the main action: he replaces.

That is a very common question.

In Arabic, the verb يستبدل already tells you the subject is he. So the sentence could simply be:

يستبدل البرغي بقطعة الغيار.

and it would still mean He replaces the screw with the spare part.

Adding هو can:

• make the subject extra clear
• add emphasis, like he replaces it
• help when the sentence is given in isolation

So هو is not always necessary, but it is completely correct.

Arabic allows more than one normal word order.

Two common patterns are:

• Verb–Subject–Object:
  يستبدل هو البرغي بقطعة الغيار
• Subject–Verb–Object:
  هو يستبدل البرغي بقطعة الغيار

In Modern Standard Arabic, both are possible, but starting with هو can sound more like He is the one who... or simply make the sentence feel more explicit.

So this sentence uses a perfectly normal subject-first structure.

Because Arabic uses the verb استبدل in a structure that matches:

replace X with Y

Here:

• البرغي = the thing being replaced
• بقطعة الغيار = the thing used as the replacement

So:

• يستبدل البرغي = he replaces the screw
• بقطعة الغيار = with the spare part

This is one of the most important things to notice in the sentence:

• the old item is the direct object
• the new item comes after بـ

So هو يستبدل البرغي بقطعة الغيار means: He replaces the screw with the spare part.

Here بـ means with.

So:

• بقطعة الغيار = with the spare part

The preposition بـ is very common in Arabic and can mean several things depending on context, such as:

• with
• by
• using
• in

But in this sentence, the natural meaning is with.

Yes.

قطعة الغيار is an iḍāfa (construct phrase), which is a very common Arabic structure.

Literally, it is something like:

• قطعة = piece / part
• الغيار = replacement

Together, it means:

• spare part
• more literally: part of replacement

In an iḍāfa:

• the first noun usually does not take ال
• the second noun can be definite, and that makes the whole phrase definite

So:

• قطعة غيار = a spare part
• قطعة الغيار = the spare part

Because that is how iḍāfa works.

In an iḍāfa:

• the first noun does not take الـ
• the second noun carries the definiteness

So:

• قطعة الغيار is definite because الغيار is definite
• the whole phrase means the spare part

This is normal Arabic grammar, even though it may look strange to an English speaker at first.

Usually, yes.

برغي means screw.

With الـ, it becomes:

• البرغي = the screw

In a practical or mechanical context, this is the ordinary word for a screw.

It can mean either one.

The Arabic present tense often covers both:

• he replaces
• he is replacing

The exact meaning depends on context.

So this sentence could be understood as:

• He replaces the screw with the spare part or
• He is replacing the screw with the spare part

If you want to make the action clearly progressive in context, Arabic often relies on surrounding words rather than changing the verb form itself.

Yes. In normal Arabic writing, short vowels and case endings are usually not written.

So you normally see:

هو يستبدل البرغي بقطعة الغيار

But in fully vowelled, formal grammar terms, it would be something like:

هو يستبدلُ البرغيَّ بقطعةِ الغيارِ

Why?

• يستبدلُ: indicative ending
• البرغيَّ: direct object, so accusative
• بقطعةِ: after the preposition بـ, so genitive
• الغيارِ: second term of iḍāfa, also genitive

Learners do not need to write these endings all the time, but it is useful to know why they are there.

A careful pronunciation would be approximately:

huwa yastabdilu al-burghiya bi-qiṭʿati l-ghiyāri

A few notes:

• هو = huwa
• يستبدل = yastabdilu
• البرغي = al-burghi
• قطعة has the consonant ʿ at the end: qiṭʿa
• الغيار = al-ghiyār

In normal pause pronunciation, case endings are often not fully pronounced, so you may hear something closer to:

huwa yastabdil al-burghi bi-qiṭʿat il-ghiyār

Arabic can express replacement in different ways, but with استبدل the pattern in this sentence is very common:

استبدل X بـ Y
= replace X with Y

So here:

• X = البرغي
• Y = قطعة الغيار

That means: He replaces the screw with the spare part.

Because English can also say things like replace X with Y and substitute Y for X, learners sometimes mix up the roles. In this Arabic structure:

• the thing after the verb is what gets removed or replaced
• the thing after بـ is the new thing

Yes, قطعة غيار is a standard and very common expression for spare part.

You may see:

• قطعة غيار = a spare part
• قطعة الغيار = the spare part

So the sentence is using normal vocabulary for a mechanical or practical context.

Yes, but it changes the meaning.

Compare:

• البرغي = the screw
• برغي = a screw

and:

• قطعة الغيار = the spare part
• قطعة غيار = a spare part

So if you remove الـ, the sentence becomes less definite and more like: He replaces a screw with a spare part.

The original sentence is definite: He replaces the screw with the spare part.