هذا القميص رقيق.

In Arabic, the present tense of to be is usually not written or spoken.

So هذا القميص رقيق literally looks like this the-shirt thin, but it means This shirt is thin.

This is a very common pattern in Arabic:

• البيت كبير = The house is big
• الجو جميل = The weather is nice

If you want was, Arabic does use a verb:

• كان القميص رقيقًا = The shirt was thin

هذا means this for a masculine singular noun.

Since قميص (shirt) is masculine singular, Arabic uses هذا:

• هذا القميص = this shirt

If the noun were feminine singular, you would usually use هذه:

• هذه السيارة = this car

So هذا is chosen because it matches the gender and number of قميص.

In standard Arabic, when you say this + noun, the noun is usually definite, so it takes الـ.

That is why you normally say:

• هذا القميص = this shirt
• هذا الكتاب = this book

This is the regular MSA pattern with demonstratives.

Arabic normally puts the description after the noun.

So:

• القميص رقيق = the shirt is thin

This is natural Arabic word order. English often uses:

• The shirt is thin

Arabic instead commonly uses:

• the shirt + thin

This happens both with predicates and with adjectives that directly modify nouns, but the grammar is not exactly the same in each case.

Great question. Here رقيق is not an adjective inside the noun phrase the thin shirt. It is the predicate of the sentence: is thin.

So:

• هذا القميص رقيق = This shirt is thin

But if you want the thin shirt, then the adjective must match the noun in definiteness:

• القميص الرقيق = the thin shirt

Compare:

• هذا القميص رقيق = This shirt is thin
• هذا القميص الرقيق = This thin shirt

So the absence of الـ on رقيق helps show that it is the predicate, not just a modifier inside the noun phrase.

Yes. As a predicate adjective, رقيق agrees with قميص in gender and number.

Since قميص is masculine singular, the predicate is also masculine singular:

• قميص رقيق

If the noun were feminine singular, you would use:

• هذه القميص؟ No, because قميص is masculine.
• A better example: هذه الورقة رقيقة = This paper is thin/delicate

Notice how رقيق becomes رقيقة for feminine singular.

So agreement still matters, even though definiteness does not match here.

With full case endings, it is:

هذا القميصُ رقيقٌ

Here is what is happening:

• القميصُ ends in ـُ because it is in the nominative
• رقيقٌ ends in ـٌ because it is also nominative as the predicate

In normal written Arabic, these short vowels are usually omitted, so you usually see:

• هذا القميص رقيق

In careful reading or grammar-focused study, the fully vowelled form is useful.

In the fully vowelled form, رقيقٌ has tanwīn because it is indefinite.

That fits the sentence pattern:

• هذا القميصُ رقيقٌ = This shirt is thin

The predicate is often indefinite in this kind of nominal sentence.

By contrast:

• الرقيق would mean the thin one or would function as a definite adjective, depending on context

So:

• رقيقٌ = indefinite predicate
• الرقيق = definite form

قميص is pronounced approximately qa-MEES.

A few points:

• ق is a deep q sound, not exactly like English k
• مي gives a long ee sound
• ص is an emphatic s

So قميص is not quite the same as kamees, even though that spelling may help beginners.

رقيق is approximately ra-QEEQ.

A few details:

• the first ر is a rolled or tapped r
• the middle vowel is long: ـيق
• the last consonant is again ق, the deep q sound

So it has two q sounds:

• رقيق = ra-qeeq

رقيق can mean things like thin, fine, delicate, or soft/fine in texture, depending on context.

With clothing or fabric, it often suggests:

• thin
• light
• delicate

So the exact English translation can vary a little depending on what is being described.

It is a nominal sentence in Arabic, because it does not begin with a verb.

Arabic has two very common sentence types:

• verbal sentences: start with a verb
• nominal sentences: start with a noun or noun-like element

Here the sentence starts with هذا, so it is a nominal sentence:

• هذا القميص رقيق

This type is very common for statements like:

• The book is new
• The room is large
• This shirt is thin

Yes.

• القميص رقيق = The shirt is thin
• هذا القميص رقيق = This shirt is thin

Adding هذا makes it more specific: you are pointing out this shirt.

So both are correct, but they mean slightly different things.