العشب مبلل في يوم غائم.

In Modern Standard Arabic, the verb to be is usually not written in the present tense.

So:

• العشب مبلل = The grass is wet

There is no separate present-tense word for is here.

But in other tenses, Arabic does use a verb:

• كان العشب مبللًا = The grass was wet
• سيكون العشب مبللًا = The grass will be wet

This kind of sentence without a present-tense is is called a nominal sentence.

The sentence has three main parts:

• العشب = the subject
• مبلل = the predicate / description
• في يوم غائم = a prepositional phrase giving time/context, roughly on a cloudy day

So the structure is:

• العشب → the grass
• مبلل → wet
• في يوم غائم → on a cloudy day

Very literally, it is something like:

• The grass, wet, on a cloudy day

In natural English, that becomes The grass is wet on a cloudy day.

الـ is the Arabic definite article, meaning the.

So:

• عشب = grass
• العشب = the grass

Arabic often uses the definite article where English might also use a more general noun. So depending on context, العشب can mean:

• the grass
• or sometimes just grass in a general sense

In this sentence, العشب is the topic being talked about, so the definite form sounds natural.

Because here مبلل is the predicate of the sentence, not an adjective attached directly to the noun.

Compare these:

• العشب مبلل = The grass is wet
• العشب المبلل = the wet grass

That is a very important difference.

In العشب مبلل:

• العشب is the subject
• مبلل tells us something about it

In العشب المبلل:

• المبلل is an adjective describing العشب
• together they form one noun phrase: the wet grass

So if you add الـ to مبلل here, you change the structure and no longer have the same sentence type.

مبلل is an adjective meaning wet.

More specifically, it comes from a verbal pattern and is related to the idea of something being made wet or moistened. In actual use, though, learners can safely treat it as a normal adjective meaning:

• wet
• damp

So in this sentence:

• العشب مبلل = The grass is wet

You do not need to analyze its root every time, but it is useful to know that Arabic often uses forms like this as adjectives.

في usually means in, but depending on context it can also mean:

• in
• on
• during

Here في يوم غائم is best understood as:

• on a cloudy day
• or during a cloudy day

Word-for-word it is:

• في = in/on/during
• يوم = day
• غائم = cloudy

So literally: in a cloudy day would sound awkward in English, but idiomatic English says on a cloudy day.

Because غائم is an adjective describing يوم, and in Arabic adjectives normally:

1. come after the noun
2. agree with the noun in definiteness, gender, number, and case

So:

• يوم = a day
• غائم = cloudy

Together:

• يوم غائم = a cloudy day

Since يوم is indefinite, the adjective غائم is also indefinite.

Compare:

• يوم غائم = a cloudy day
• اليوم الغائم = the cloudy day

So the lack of الـ on both words is exactly what we expect here.

With full case endings, it would be written:

العُشْبُ مُبَلَّلٌ في يَوْمٍ غائِمٍ

These endings show grammar:

• العشبُ → nominative, because it is the subject
• مبللٌ → nominative, because it is the predicate of a nominal sentence
• في يومٍ → يومٍ is genitive because it comes after the preposition في
• غائمٍ → genitive too, because it agrees with يومٍ

In everyday unvowelled writing, these short vowels are usually omitted, so you normally see:

العشب مبلل في يوم غائم

Yes. Arabic is flexible, especially with prepositional phrases like في يوم غائم.

You can also say:

في يوم غائم، العشب مبلل.

That still means:

• On a cloudy day, the grass is wet

Putting في يوم غائم first gives it more emphasis, like setting the scene before the main statement.

Both orders are natural, but:

• العشب مبلل في يوم غائم focuses first on the grass
• في يوم غائم، العشب مبلل focuses first on the time/context