Learn Hardcore Malay: Teman saya yang tinggi duduk di belakang kelas. - My friend who is tall sits at the back of the class.

kawan is more common in casual speech for friend.
teman sounds a bit more formal, or sometimes slightly literary/romantic, depending on context.
Both can usually be translated as friend, and teman saya / kawan saya both mean my friend.

So the sentence could also be said as Kawan saya yang tinggi duduk di belakang kelas, with almost the same meaning and tone (just slightly more colloquial with kawan).

What does yang do in teman saya yang tinggi?

yang introduces a descriptive clause or phrase that explains or identifies a noun. Here:

teman saya = my friend
yang tinggi = who is tall / that is tall

So teman saya yang tinggi means:

my friend who is tall
or, more naturally in English:
my tall friend

In grammar terms, yang is marking a relative clause or descriptive phrase. It links teman saya with the description tinggi.

Without yang, teman saya tinggi would just be a full sentence: My friend is tall.
With yang, teman saya yang tinggi becomes a noun phrase: the friend of mine who is tall.

Why is tinggi after the noun? Can I say tinggi teman saya?

In Malay, adjectives usually come after the noun:

teman tinggi = tall friend
rumah besar = big house
kereta merah = red car

So:

teman saya yang tinggi follows the normal order: noun + (possessor) + yang + adjective.

Saying tinggi teman saya is not normal for “my tall friend.”
Tinggi teman saya by itself would be understood more as a sentence fragment like (how) tall my friend is, not as a noun phrase.

Correct patterns:

Teman saya tinggi. = My friend is tall. (full sentence: subject + adjective)
Teman saya yang tinggi … = My friend who is tall … (noun phrase followed by more info)

What is the difference between Teman saya yang tinggi duduk di belakang kelas and Teman saya tinggi dan duduk di belakang kelas?

Both can be translated with similar English, but the structure and nuance are different.

Teman saya yang tinggi duduk di belakang kelas.
- Literally: My friend who is tall sits at the back of the class.
- yang tinggi directly picks out the tall friend (of mine) from possibly several friends.
- It feels like you are identifying a particular friend by their tallness.
Teman saya tinggi dan duduk di belakang kelas.
- Literally: My friend is tall and sits at the back of the class.
- Here, tinggi and duduk di belakang kelas are just two separate facts about the same friend.
- It doesn’t sound like you are using tallness to distinguish which friend you mean; you’re simply listing two characteristics.

If you imagine you have several friends and only one is tall:

Teman saya yang tinggi duduk di belakang kelas. = The tall one sits at the back.

Could teman saya yang tinggi mean “the tall one among my friends”? Or is it only one friend?

Malay does not mark singular vs plural on nouns, so teman saya can mean:

my friend
or
my friends, depending on context.

So teman saya yang tinggi can mean:

my friend who is tall (if context clearly refers to one person), or
my friends who are tall (if context is plural).

In isolation, without context, most learners will first read it as singular (my friend), but native speakers rely on the broader conversation to know if it’s one or many.

Why do we need yang? Can I just say Teman saya tinggi duduk di belakang kelas?

You cannot just drop yang here.

Teman saya tinggi = My friend is tall.
Teman saya tinggi duduk di belakang kelas sounds ungrammatical because tinggi is left hanging between the subject and the verb duduk.

To turn tinggi into a descriptive phrase that belongs to the noun, Malay uses yang:

Teman saya yang tinggi = my friend who is tall / my tall friend

Then you can add the rest:

Teman saya yang tinggi duduk di belakang kelas.
= My tall friend sits at the back of the class.

So yang is necessary here to form that “who is tall” structure.

What exactly does di belakang kelas mean? Is it “behind the class” or “at the back of the classroom”?

Literally, di belakang kelas means at the back of the class or behind the class.

di = at / in / on (general location preposition)
belakang = back / behind
kelas = class / classroom (depends on context)

In normal classroom context, di belakang kelas is usually understood as at the back (seats) of the classroom, not outside behind the building.

If you specifically meant outside, behind the classroom building, context or extra words are usually added, for example:

di belakang bangunan kelas = behind the classroom building

Would di belakang kelas saya be more correct for “at the back of my class”?

di belakang kelas is already natural and acceptable when it’s obvious we’re talking about your class or the class you are in.

You can say:

di belakang kelas saya = at the back of my class (more explicit)
di belakang kelas = at the back of the class (possessor left understood from context)

In conversation, if it’s clear whose class you’re talking about, speakers often just say di belakang kelas. Adding saya is grammatically fine, but not required.

What is the function of duduk here? Is it like the English “sit” or more like “is sitting”?

duduk means to sit / sit(s) / is sitting, depending on context.

Malay verbs do not change form for tense or aspect. So:

Teman saya yang tinggi duduk di belakang kelas.
Could be translated as:
- My tall friend sits at the back of the class.
- My tall friend is sitting at the back of the class.

Which one is used in English depends on the situation or time reference in the conversation, not on any change in the Malay verb form.

How would I say “My tall friend sits at the front of the class” instead?

You mainly change belakang (back) to depan (front):

Teman saya yang tinggi duduk di depan kelas.

Breakdown:

teman saya = my friend
yang tinggi = who is tall / the tall one
duduk = sits / is sitting
di depan = at the front
kelas = class / classroom

So di depan kelas = at the front of the class.