يرى صديقي شجرة كبيرة.

Because this is a verbal sentence in Arabic, and a very common word order is:

verb + subject + object

So:

• يرى = sees
• صديقي = my friend
• شجرة كبيرة = a big tree

This VSO order (verb-subject-object) is very normal in Modern Standard Arabic.

English usually prefers subject + verb + object, but Arabic often begins with the verb.

يرى is the 3rd person masculine singular imperfect form of the verb رأى.

So it means:

• he sees
• he is seeing

In this sentence, the he is صديقي.

A useful point: the dictionary form is often given as رأى (to see / he saw), but the present/imperfect form changes shape and becomes يرى.

It is pronounced roughly yarā.

In Arabic verbal sentences, when the verb comes before the subject, the verb is typically kept in the singular form.

Here the subject صديقي is singular anyway, so the form matches naturally:

• يرى = he sees
• صديقي = my friend

If the subject were plural and came after the verb, Arabic would still often use a singular verb in this verb-first pattern. That is a common feature of Arabic grammar.

The base noun is صديق = friend.

When you add ـي, it means my:

• صديق = friend
• صديقي = my friend

So the ending ـي is a possessive suffix meaning my.

This is very common in Arabic:

• كتابي = my book
• بيتي = my house
• صديقي = my friend

Because it means a tree, not the tree.

In Arabic:

• شجرة = a tree / tree
• الشجرة = the tree

So this sentence is talking about an indefinite tree, not a specific one already known to the listener.

In fully vowelled Arabic, the direct object here would usually be written:

شجرةً

That final ً helps show indefiniteness and accusative case, but short vowels are often omitted in normal writing.

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

So:

• شجرة كبيرة = a big tree
• literally: tree big

This is the normal noun + adjective order in Arabic.

Compare:

• بيت كبير = a big house
• سيارة سريعة = a fast car
• شجرة كبيرة = a big tree

Because شجرة is a feminine noun, and Arabic adjectives must agree with the noun they describe.

So the adjective must match the noun in:

• gender
• number
• definiteness
• case

Here:

• شجرة is feminine singular
• so the adjective is كبيرة, also feminine singular

If the noun were masculine, you would use كبير instead:

• كتاب كبير = a big book
• شجرة كبيرة = a big tree

Because the noun phrase means a big tree, not the big tree.

In Arabic, the adjective must match the noun in definiteness too.

So:

• شجرة كبيرة = a big tree
  both are indefinite

but:

• الشجرة الكبيرة = the big tree
  both are definite

You cannot normally mix them like this in a simple adjective phrase:

• الشجرة كبيرة does not mean the big tree
  It usually means the tree is big

So matching definiteness is very important.

The sentence is:

يَرَى صَدِيقِي شَجَرَةً كَبِيرَةً

The roles are:

• يرى = verb
• صديقي = subject
• شجرةً = direct object
• كبيرةً = adjective describing the direct object

So grammatically:

• صديقي is the subject of the verb
• شجرةً is the object being seen
• كبيرةً agrees with شجرةً

In a fully vowelled version:

• شجرةً is accusative
• كبيرةً is also accusative because it follows and matches شجرة

With صديقي, the nominative role is there, but the ending is not clearly visible because of the attached ـي.

In normal Arabic writing, short vowels and many case endings are usually not written.

So you often see:

يرى صديقي شجرة كبيرة

But the fully vowelled form would be:

يَرَى صَدِيقِي شَجَرَةً كَبِيرَةً

These written vowels help learners see things like:

• pronunciation
• case
• indefiniteness
• adjective agreement

Native readers usually understand the sentence from context even without those marks.

Yes. That is also grammatical.

It changes the word order to subject + verb + object, which is more like English:

• صديقي يرى شجرة كبيرة

This can place a little more focus on my friend as the topic.

So both are possible:

• يرى صديقي شجرة كبيرة = common verb-first structure
• صديقي يرى شجرة كبيرة = subject-first structure

In this particular sentence, both sound natural.