يضيء المصباح اليدوي الغرفة.

يضيء is a present/imperfect verb form. Here it means he/it illuminates or he/it lights up.

More specifically, it is:

• 3rd person
• masculine
• singular

That matches المصباح because مصباح is a masculine singular noun.

The dictionary form is أضاء = to illuminate / to light up.

It is pronounced roughly yuḍīʾu.

A few points:

• ض is an emphatic d-type sound.
• يضيـ gives you a long ee sound.
• The final ء is a hamza, a glottal stop, so the word does not just flow straight through at the end.

So the ending is something like -eeʾu, not just -eeu.

In fully vocalized form, it is يُضِيءُ.

Because verb–subject–object word order is very common in Modern Standard Arabic.

So:

• يضيء = illuminates
• المصباح اليدوي = the flashlight
• الغرفة = the room

This verb-first pattern is completely normal.

You can also say:

المصباح اليدوي يضيء الغرفة

That is also correct, but it shifts the emphasis a bit toward the flashlight as the topic.

There are two main clues:

1. Meaning

   • The flashlight is doing the action.
   • The room is receiving the action.

2. Case endings in fully vocalized Arabic

   • المصباحُ اليدويُّ is nominative → subject
   • الغرفةَ is accusative → direct object

So the fully vocalized sentence is:

يُضِيءُ المِصْبَاحُ اليَدَوِيُّ الغُرْفَةَ

Even if short vowels are not written in everyday text, they are still part of the grammar.

Because in Arabic, adjectives normally come after the noun they describe.

So:

• مصباح = lamp
• يدوي = hand-held / manual
• مصباح يدوي = a flashlight

This is the normal Arabic order:

• noun first
• adjective second

So Arabic says something structurally like lamp hand-held, not hand-held lamp.

Here it is a noun + adjective phrase, not an iḍāfa.

Why?

Because اليدوي is an adjective meaning something like hand-held, manual, or operated by hand, and it agrees with المصباح.

Signs that it is an adjective here:

• both words can be definite: المصباح اليدوي
• the adjective matches the noun in:
  • definiteness
  • gender
  • number
  • case

If it were an iḍāfa, the structure would work differently, and you would not normally have الـ on both parts in this way.

Because Arabic adjectives must agree with the nouns they describe in definiteness.

So if the noun is definite:

• المصباح = the lamp

then the adjective must also be definite:

• اليدوي = the hand-held/manual

That is why Arabic says:

المصباح اليدوي

literally something like the lamp the-hand-held, which simply means the hand-held lamp / the flashlight.

If it were indefinite, you would say:

مصباح يدوي = a flashlight

Because الغرفة is the direct object of the verb يضيء.

The verb أضاء / يضيء can take a direct object directly, just like English illuminate:

• يضيء الغرفة = it illuminates the room

So Arabic does not need a preposition like في here.

Compare:

• يضيء الغرفة = it lights up the room
• في الغرفة = in the room

Those are different ideas.

In careful fully vocalized MSA, the sentence is:

يُضِيءُ المِصْبَاحُ اليَدَوِيُّ الغُرْفَةَ

The endings are:

• يُضِيءُ → -u
  indicative verb ending

• المِصْبَاحُ → -u
  nominative, because it is the subject

• اليَدَوِيُّ → -u
  nominative too, because it is an adjective describing the subject

• الغُرْفَةَ → -a
  accusative, because it is the direct object

In normal unvoweled writing, these short vowels are usually omitted, but learners should still know they are there grammatically.