هي تضيف مسحوق الغسيل.

هي is the independent pronoun meaning she.

In this sentence, it makes the subject explicit: هي تضيف = she adds.

In Arabic, the verb تضيف already shows a feminine third-person subject, so هي is often optional. You could also say just تضيف مسحوق الغسيل if the context already makes it clear who she is.

Including هي can:

• make the sentence clearer
• add emphasis
• contrast with someone else, such as هو = he

تضيف is the present-tense verb here, meaning she adds.

The dictionary form is أضافَ = to add.

So:

• أضافَ = he added
• يُضيفُ = he adds / he is adding
• تُضيفُ = she adds / she is adding

Like many Arabic present forms, it can correspond to both simple present and present progressive in English, depending on context.

In the Arabic present tense, the first letter often shows the person and sometimes the gender.

Here:

• يضيف = he adds
• تضيف = she adds

So the تـ at the beginning tells you this is the feminine third-person singular form.

One thing that can confuse learners: تضيف can also mean you add when talking to one man. That is why including هي helps remove ambiguity.

تضيف comes from the verb أضافَ, which is a Form IV verb.

Its root is usually analyzed as ض ي ف.

A useful set of forms is:

• past: أضافَ
• present: يُضيفُ
• verbal noun: إضافة
• active participle: مُضيف

Form IV often has a causative or transitive sense, and here أضافَ means to add something.

Because this is an iḍāfa construction, often called a construct phrase.

مسحوق الغسيل literally works like:

• powder of the washing/laundry

In an iḍāfa:

• the first noun normally does not take ال
• the second noun determines whether the whole phrase is definite or indefinite

So:

• مسحوق الغسيل = the washing powder / laundry detergent
• the first word مسحوق does not take ال because it is the first part of the iḍāfa

This is one of the most important noun structures in Arabic.

مسحوق literally means powdered or powder.

It comes from the root س ح ق, which has the idea of grinding or crushing.

In everyday usage, مسحوق is commonly used as a noun meaning powder, especially in product names and household vocabulary.

So in مسحوق الغسيل, it means washing powder or laundry detergent powder.

الغسيل means the washing, the laundry, or washing/laundry depending on context.

In this phrase, مسحوق الغسيل is an established combination meaning:

• washing powder
• laundry detergent

So even though the words are literally something like powder of the laundry, the natural meaning is the product used for washing clothes.

With full vowels and case endings, it would be:

هِيَ تُضِيفُ مَسْحُوقَ الغَسِيلِ

Here is why:

• هِيَ = pronoun
• تُضِيفُ ends in ـُ because it is a present-tense indicative verb
• مَسْحُوقَ ends in ـَ because it is the direct object, so it is accusative
• الغَسِيلِ ends in ـِ because it is the second term of an iḍāfa, so it is genitive

In normal everyday writing, these short vowels are usually not written.

A careful MSA pronunciation would be roughly:

hiya tuḍīfu masḥūqa l-ghasīli

If you ignore case endings, as people often do in less formal pronunciation, you may hear something closer to:

hiya tuḍīf masḥūq al-ghasīl

A few sound notes:

• ض in تضيف is an emphatic d
• ح in مسحوق is a strong breathy sound, not the normal English h
• غ in الغسيل is a guttural sound somewhat like the French or German r

Yes. Very often, Arabic leaves the subject pronoun out because the verb already contains that information.

So all of these are possible depending on context:

• هي تضيف مسحوق الغسيل
• تضيف مسحوق الغسيل

The version with هي is more explicit. The version without it is very natural when the subject is already understood.

No. Arabic allows more than one word order.

This sentence is subject + verb + object:

• هي تضيف مسحوق الغسيل

But Arabic also commonly uses verb + subject + object, especially with full noun subjects:

• تضيفُ المرأةُ مسحوقَ الغسيلِ

With a pronoun subject, Arabic often just uses the verb alone:

• تضيف مسحوق الغسيل

So the sentence you were given is correct, but it is not the only possible order.

Yes, it is a natural and common MSA expression for washing powder or laundry detergent.

Depending on region or product type, you may also see other expressions, but مسحوق الغسيل is standard and widely understood.

If you want to make the action more specific, Arabic often adds a destination:

• هي تضيف مسحوق الغسيل إلى الغسالة = she adds the laundry detergent to the washing machine
• هي تضيف مسحوق الغسيل إلى الماء = she adds the laundry detergent to the water

Without that extra phrase, the sentence is still grammatically complete.