صديقي يزرع الشتلة في المساحة الخضراء.

Because صديقي is made of:

• صديق = friend
• ـي = the suffix meaning my

So صديقي literally means my friend.

This suffix is attached directly to the noun in Arabic. A native English speaker can think of it as something like friend-my, even though the natural English translation is my friend.

يزرع is the imperfect (non-past) form of the verb زرع = to plant / to cultivate.

Here it is third person masculine singular, because the subject is صديقي = my friend, which is grammatically masculine singular.

So:

• يزرع = he plants / he is planting

If the subject were feminine, the verb would usually change to تزرع.

It can mean either one, depending on context.

In Modern Standard Arabic, the imperfect form often covers meanings that English splits into:

• he plants
• he is planting
• sometimes even he will plant, if the context makes that clear

So يزرع does not by itself force just one English tense. The surrounding context tells you whether it is habitual, happening now, or future.

Arabic allows more than one normal word order.

This sentence uses subject–verb–object order:

• صديقي = subject
• يزرع = verb
• الشتلة = object

But Arabic also often uses verb–subject–object, so you could also say:

• يزرع صديقي الشتلة في المساحة الخضراء.

Both are grammatical. Starting with the subject can feel a bit more straightforward for learners and can put slight emphasis on my friend.

Because it has الـ, the Arabic definite article, which usually means the.

So:

• شتلة = a seedling / a sapling
• الشتلة = the seedling / the sapling

Since the meaning has already been given to the learner, the important grammar point is that الـ makes the noun definite.

Also, in this sentence الشتلة is the direct object of يزرع.

في means in.

So:

• في المساحة الخضراء = in the green area/space

A very important grammar point is that في is a preposition, and prepositions make the following noun genitive in Arabic.

So in full case-marked Arabic, المساحة would take a genitive ending.

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

So:

• المساحة = the area / the space
• الخضراء = green

Together:

• المساحة الخضراء = the green area

This is the normal Arabic order: noun + adjective, not adjective + noun as in English.

Because Arabic adjectives usually match the noun they describe in definiteness.

So if the noun is definite, the adjective is also definite:

• المساحة = the area
• الخضراء = the green

That is why Arabic says:

• المساحة الخضراء

not:

• المساحة خضراء in this sentence

The version without الـ on the adjective would usually not work as a normal attributive phrase here.

Because المساحة is a feminine singular noun, and the adjective must agree with it.

The masculine form is:

• أخضر = green (masculine)

The feminine form is:

• خضراء = green (feminine)

So since مساحة is feminine, Arabic uses:

• المساحة الخضراء

This is part of normal adjective agreement in Arabic: adjectives agree with the noun in gender, number, and definiteness.

A fully vowelled version would be:

صديقي يزرعُ الشتلةَ في المساحةِ الخضراءِ.

The endings show the grammar:

• يزرعُ: indicative/imperfect ending
• الشتلةَ: accusative, because it is the direct object
• المساحةِ: genitive, because it comes after في
• الخضراءِ: genitive too, because it follows المساحة as its adjective

As for صديقي, it is the subject, so it is nominative in function, although the case ending is not obvious here because of the attached ـي.

In normal everyday Arabic writing, these short vowel endings are usually omitted.

It is not pronounced the same way in every word.

In الشتلة, the first letter after الـ is ش, which is a sun letter. That means the ل sound of الـ assimilates, so the word is pronounced roughly like ash-sh..., not al-sh....

But in:

• المساحة
• الخضراء

the first letters (م and خ) are moon letters, so the ل sound is pronounced normally.

So this sentence gives you both patterns:

• الشتلة → sun-letter pronunciation
• المساحة, الخضراء → moon-letter pronunciation

You would change both the noun and the verb:

• صديقتي تزرع الشتلة في المساحة الخضراء.

Why?

• صديقتي = my female friend
• تزرع = she plants / she is planting

So the subject becomes feminine, and the verb changes to the feminine singular form.