الصبار في ضوء الشمس.

In careful MSA pronunciation, it is:

aṣ-ṣabbāru fī ḍawʾi ash-shamsi

A fully vowelled version would be:

الصبّارُ في ضَوْءِ الشَّمْسِ

A few important points:

• الصبار is pronounced aṣ-ṣabbār, not al-ṣabār
• الشمس is pronounced ash-shams
• الصبّار has a doubled b sound because of the shadda: bb
• ضوء is pronounced roughly ḍawʾ, with a short stop at the end because of the hamza ء

In pause, speakers often drop the final case vowels, so you may also hear something closer to:

aṣ-ṣabbār fī ḍawʾ ash-shams

Because Arabic usually does not use a present-tense form of to be in simple sentences like this.

So:

• الصبار في ضوء الشمس
  literally looks like the cactus in the sunlight
• but naturally means The cactus is in the sunlight

This is a nominal sentence in Arabic:

• الصبّارُ = the subject
• في ضوء الشمس = the predicate, here a prepositional phrase

In past or future contexts, Arabic would use a form of كان or another verb if needed.

في means in.

It is a very common preposition in Arabic, and it makes the following noun genitive.

So in this sentence:

• في ضوءِ = in the light of...

Because في is a preposition, ضوء takes the genitive case in full vocalization:

• ضوءِ

It is an iḍāfa construction, often called a construct phrase.

Literally, it means:

• ضوء = light
• الشمس = the sun

Together:

• ضوء الشمس = the light of the sun

In natural English, that becomes sunlight or the sunlight, depending on context.

So the structure is:

• first noun: ضوء
• second noun: الشمس

The second noun explains or possesses the first:
light of the sun

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

So Arabic says:

• ضوء الشمس

not:

• الضوء الشمس

This is a key rule of iḍāfa:

• the first noun does not take ال
• the whole phrase becomes definite if the second noun is definite

Since الشمس is definite, ضوء الشمس is also definite.

That is why ضوء الشمس can mean the sunlight even though ضوء itself has no ال.

Because ش and ص are both sun letters.

When ال comes before a sun letter, the l sound of al- is not pronounced. Instead, the following consonant is doubled.

So:

• الشمس is pronounced ash-shams
• الصبّار is pronounced aṣ-ṣabbār

This happens in pronunciation, but the spelling still keeps ال.

So Arabic writes:

• الشمس
• الصبار

but pronounces them with assimilation.

In full grammatical reading, the phrase is:

في ضوءِ الشمسِ

Both nouns are in the genitive here, but for different reasons:

• ضوءِ is genitive because it comes after the preposition في
• الشمسِ is genitive because it is the second term of an iḍāfa

So:

• في
  • noun = genitive
• second noun in iḍāfa = genitive

That is why the careful form is:

في ضوءِ الشمسِ

The word ضوء contains a hamza ء, which represents a brief glottal stop.

So ضوء is pronounced approximately:

ḍawʾ

You can think of it as:

• ḍaw
  • a quick stop in the throat

When case endings are pronounced, you get:

• ḍawʾu
• ḍawʾa
• ḍawʾi

In this sentence, after في, it is:

• ḍawʾi

This word can be tricky for English speakers because the hamza comes after aw.

Because Arabic often starts a nominal sentence with the topic or subject.

Here:

• الصبّارُ = the topic/subject
• في ضوء الشمس = what is being said about it

So the structure is:

• The cactus
  • is in the sunlight

This is very natural Arabic word order for a simple nominal sentence.

It can be understood as a full sentence:

• The cactus is in the sunlight

But depending on context, it could also work like a caption or label:

• The cactus in the sunlight

Arabic often allows this kind of ambiguity when there is no written vowel marking and no extra context.

In ordinary reading, though, many learners will treat it as a full nominal sentence, which is a very useful interpretation.