Khỉ ở trên cây.

Vietnamese usually does not require articles the way English does. So:

• khỉ can mean monkey, a monkey, or the monkey
• cây can mean tree, a tree, or the tree

The exact meaning depends on context. If you need to be more specific, Vietnamese can add other words, but in a simple sentence like this, leaving articles out is completely normal.

Ở often means to be at / to stay / to live at, depending on context.

In Khỉ ở trên cây, ở marks location, so it works a bit like English is located:

• khỉ = monkey
• ở = is at / is located
• trên cây = on the tree

So ở is doing an important job here: it tells you where the monkey is.

Trên means on, above, or over, depending on context.

In this sentence, trên cây means on the tree or more naturally in English, often in the tree, because English describes animals as being in a tree more often than on a tree.

So Vietnamese uses trên based on spatial position, while English may choose in or on depending on what sounds natural.

They do different jobs:

• ở says that something is located
• trên tells you where it is relative to something else: on/above

So the structure is:

• [noun] + ở + [location]

and here the location is:

• trên cây = on the tree

Together, ở trên cây means is on the tree.

In everyday speech, Vietnamese speakers may sometimes shorten things depending on context, but ở trên is a very normal and clear combination.

Vietnamese basic word order is often similar to English:

• subject + verb/location marker + place

So:

• Khỉ = subject
• ở = location verb/marker
• trên cây = place

That gives:

• Khỉ ở trên cây = The monkey is on the tree

You can move location phrases around in some cases for emphasis, but the most neutral order is the one in the sentence.

Often, yes—con khỉ is very common when talking about an animal as an individual creature.

• con is a classifier commonly used for animals
• con khỉ = a monkey / the monkey

So:

• Khỉ ở trên cây is understandable and grammatical
• Con khỉ ở trên cây may sound more natural in many everyday situations

Using just khỉ can sound more general, like talking about monkeys as a type, or it may simply be a shorter textbook-style sentence.

Here, cây means tree as a noun.

Vietnamese also uses cây as a classifier for certain long, stick-like, or plant-related objects, but in trên cây, it is simply the noun tree.

So in this sentence:

• cây = tree

This is not a classifier use.

By itself, khỉ does not clearly show singular or plural. It can mean:

• a monkey
• the monkey
• monkeys

Context tells you which one is intended.

If you want to make plurality clearer, Vietnamese can add words such as:

• những con khỉ = monkeys
• mấy con khỉ = a few monkeys

But in a short sentence like this, khỉ alone is normal.

A rough guide:

• khỉ: the kh is like a breathy k sound; the ỉ has the hỏi tone
• ở: has the ngã tone in standard spelling
• trên: starts with tr, which is different from English ch or j
• cây: has the ngang tone (level, no accent mark on the vowel with the circumflex and y combination)

A very rough English-style approximation is something like:

• khee uh tren cay

But that is only approximate. The tones matter a lot, and English spelling cannot represent them well.

In Vietnamese, trên cây literally points to a position on/above the tree. But in natural English, when an animal is sitting among the branches, we usually say:

• The monkey is in the tree

So depending on context:

• literal translation: The monkey is on the tree
• more natural English in many situations: The monkey is in the tree

This is a good example of how languages do not always divide space in exactly the same way.

Sometimes you may hear shortened phrases like that, especially in captions, labels, or very informal speech. But as a full basic sentence, Khỉ ở trên cây is clearer and more standard for learners.

Compare:

• Khỉ ở trên cây = The monkey is on/in the tree
• Khỉ trên cây = monkey on the tree / monkeys in the tree

Without ở, it can sound more like a noun phrase or a shortened statement rather than a full, neutral sentence.

Yes. Khỉ ở trên cây. is a complete, grammatical sentence.

That said, many native speakers might more naturally say:

• Con khỉ ở trên cây.

because con khỉ sounds like a specific animal rather than just the general noun monkey.

So your sentence is correct, but Con khỉ ở trên cây may feel more natural in everyday conversation.