Tôi hỏi tuổi của cô ấy.

Vietnamese often follows a straightforward subject + verb + object pattern:

• Tôi = subject
• hỏi = verb
• tuổi của cô ấy = object

So the sentence is literally something like I ask [the age of her].

English prefers I ask her age or I ask about her age, but Vietnamese commonly builds possession with của, so tuổi của cô ấy means her age.

Yes. Hỏi basically means to ask.

Depending on context, it can mean:

• ask someone a question
• ask about something
• inquire about something

In this sentence, hỏi tuổi của cô ấy means asking about her age. Vietnamese does not always need an extra word like English about.

Yes. Tuổi means age.

So:

• hỏi tuổi = ask someone’s age
• tuổi của cô ấy = her age

This is different from English, where we often say How old is she? or I asked her age. Vietnamese uses the noun tuổi very naturally in this kind of expression.

Của is a very common word used to show possession or association, similar to of or 's in English.

So:

• tuổi của cô ấy = the age of her = her age

It links tuổi and cô ấy.

A learner-friendly way to think about it is:

• X của Y = Y’s X / the X of Y

Examples:

• nhà của tôi = my house
• tên của anh ấy = his name
• tuổi của cô ấy = her age

Cô ấy means she / her, referring to a female person.

Breakdown:

• cô = woman / young lady / she, depending on context
• ấy = that, used here to point to a previously known person

Together, cô ấy works like she/her.

If you say only cô, it may sound more like a noun meaning the woman, the lady, or a kinship-style pronoun depending on context. Adding ấy makes it clearer that you mean that woman / she.

This sentence is grammatical and understandable, but in everyday speech, many speakers would more naturally say:

• Tôi hỏi cô ấy bao nhiêu tuổi.
• Tôi hỏi cô ấy mấy tuổi.

Those literally mean something like I asked her how many years old.

So Tôi hỏi tuổi của cô ấy is correct, but it can sound a bit more formal, written, or indirect than the more conversational versions above.

Not in this exact structure.

If you want to say her age as a noun phrase, của is what connects tuổi and cô ấy:

• tuổi của cô ấy = her age

Without của, tuổi cô ấy would usually sound incomplete or unnatural in standard Vietnamese.

However, Vietnamese often avoids this whole structure by switching to a different pattern, such as:

• Tôi hỏi cô ấy bao nhiêu tuổi.

So while của is needed in tuổi của cô ấy, the entire phrase can be replaced by a more natural alternative.

You usually do not know from the sentence alone.

Vietnamese verbs do not change form for tense the way English verbs do. Hỏi can mean:

• ask
• asked
• am asking
• was asking
• will ask

The time is understood from context or from time words, for example:

• Hôm qua tôi hỏi tuổi của cô ấy. = Yesterday I asked her age.
• Bây giờ tôi hỏi tuổi của cô ấy. = Now I’m asking her age.
• Ngày mai tôi sẽ hỏi tuổi của cô ấy. = Tomorrow I will ask her age.

So in the original sentence, tense is neutral unless context tells you more.

Not always. Vietnamese pronouns depend a lot on age, relationship, and social situation.

Tôi is a safe, neutral way to say I in many situations, especially with people you do not know well or in standard textbook Vietnamese.

But in real life, speakers may use other words for I, such as:

• mình
• em
• anh
• chị
• con
• cháu

So tôi is correct, but it is not the only possible first-person pronoun.

Vietnamese possession works differently from English.

English says:

• her age

Vietnamese often says:

• tuổi của cô ấy
  literally: age of her

So instead of changing she into her, Vietnamese keeps the noun/pronoun phrase cô ấy and uses của to show possession.

That is why you do not see a special possessive form like English her here.

Yes, in practical meaning, that is exactly what it refers to.

Even though the structure is literally I ask her age, the real-world meaning is the same as:

• I ask how old she is
• I asked her age

Vietnamese often uses the noun tuổi where English might prefer an adjective phrase like how old. So the grammar looks different, but the meaning matches.