سعر هذا القميص منخفض اليوم.

A word-by-word breakdown is:

• سعر = price
• هذا = this
• القميص = the shirt
• منخفض = low
• اليوم = today

So the whole sentence means The price of this shirt is low today.

A simple pronunciation guide is: siʿr hādhā al-qamīṣ munkhafiḍ al-yawm.

In Arabic, the present tense often does not use a separate word for is / am / are in simple statements.

So:

• سعر هذا القميص منخفض اليوم = The price of this shirt is low today

There is no present-tense copula here. This is very normal in Arabic.

If you wanted the past, you would use a verb such as كان:

• كان سعر هذا القميص منخفضًا أمس = The price of this shirt was low yesterday

When a demonstrative like هذا means this + noun in Modern Standard Arabic, the noun is usually definite with الـ:

• هذا القميص = this shirt
• هذه السيارة = this car

By contrast:

• هذا قميصٌ usually means This is a shirt

So هذا القميص is a noun phrase, while هذا قميص is more like a full sentence.

This is because Arabic is using a possession/association structure called iḍāfa.

• سعر هذا القميص literally looks like price of this shirt
• English translates it naturally as the price of this shirt

In an iḍāfa:

• the first noun usually does not take الـ
• the whole phrase can still be definite if the second part is definite

So:

• سعر هذا القميص = the price of this shirt

Even though سعر has no الـ, the whole phrase is definite because هذا القميص is definite.

It describes سعر.

The sentence is about the price, not about the shirt itself.

So the structure is:

• سعر هذا القميص = the subject, the price of this shirt
• منخفض = the predicate, low

That means:

• The price is low

It does not mean the shirt itself is low.

Because it matches سعر, which is masculine singular.

In Arabic, words that describe or refer back to a noun usually agree with that noun in gender and number. Since:

• سعر is masculine singular

the predicate is also masculine singular:

• منخفض

If the noun were feminine, the form would change. For example:

• درجة الحرارة منخفضة = The temperature is low

Because here منخفض is the predicate of the sentence, not an adjective inside a definite noun phrase.

Compare these:

• السعر منخفض = The price is low
• السعر المنخفض = the low price

In the first one, منخفض is saying something about السعر, so it stays indefinite.

In the second one, المنخفض is an adjective directly attached to السعر, so it becomes definite too.

اليوم means today and functions as an adverb of time.

In this sentence, it tells us when the price is low:

• سعر هذا القميص منخفض اليوم = The price of this shirt is low today

It often comes at the end, but Arabic word order is somewhat flexible. You could also say:

• اليوم سعر هذا القميص منخفض

This also means Today, the price of this shirt is low, but it puts more emphasis on today.

In fully vocalized MSA, the sentence is:

• سِعْرُ هٰذَا القَمِيصِ مُنْخَفِضٌ اليَوْمَ

The endings are there because of grammar:

• سعرُ = nominative, because it is the subject
• القميصِ = genitive, because it is part of the iḍāfa structure
• منخفضٌ = nominative, because it is the predicate
• اليومَ = accusative, as an adverbial expression of time

In normal writing, these short vowel endings are usually omitted, and in pause they are often not pronounced fully.

Both can relate to low cost, but they are not exactly the same.

• منخفض = low, often used with things like price, level, rate, temperature
• رخيص = cheap / inexpensive

So:

• سعر هذا القميص منخفض = The price of this shirt is low
• هذا القميص رخيص = This shirt is cheap

In your sentence, منخفض is especially natural because the subject is price.

For a yes/no question, you can add هل:

• هل سعر هذا القميص منخفض اليوم؟
• Is the price of this shirt low today?

To make it negative, you can use ليس:

• سعر هذا القميص ليس منخفضًا اليوم
• The price of this shirt is not low today

Notice that after ليس, the predicate is often written with the appropriate ending in full MSA:

• منخفضًا

In standard written Arabic, the normal MSA order is:

• هذا القميص = this shirt

The order:

• القميص هذا

is common in some spoken dialects, but it is not the usual neutral MSA form.

So for Modern Standard Arabic, stick with:

• هذا القميص