An đã chọn sách làm quà vì cô ấy biết Lan thích đọc.

đã is a past-time marker. It tells you that the action chọn (choose) happened before now.

So:

• An đã chọn sách... = An chose / has chosen books/a book...

Vietnamese does not change the verb form the way English does, so words like đã, đang, and sẽ are often used to show time:

• đã = past
• đang = ongoing / in progress
• sẽ = future

That said, in natural Vietnamese, đã can sometimes be omitted if the time is already clear from context.

Vietnamese does not use articles like a, an, or the the way English does. Nouns also usually do not change form for singular vs. plural.

So sách can mean:

• a book
• the book
• books
• the books

The exact meaning depends on context.

If the speaker wants to be more specific, they might add a classifier or another word:

• một cuốn sách = a book
• những cuốn sách = books
• cuốn sách đó = that book

In this sentence, sách is left general, which is very normal in Vietnamese.

làm quà literally means to serve as a gift or as a present.

So:

• chọn sách làm quà = choose book(s) as a gift

Here, làm does not mean make in the usual English sense. Instead, it means something like use as or have the function of.

You will see this pattern in other sentences too:

• lấy hoa làm quà = take flowers as a gift
• dùng khăn làm băng = use a scarf as a bandage

So in this sentence, An chose books to give as a present.

vì means because.

It introduces the reason for the earlier action:

• An đã chọn sách làm quà = what An did
• vì cô ấy biết Lan thích đọc = why An did it

So the structure is:

• main clause + vì + reason clause

Examples:

• Tôi ở nhà vì trời mưa. = I stayed home because it rained.
• Cô ấy học chăm vì muốn đỗ kỳ thi. = She studies hard because she wants to pass the exam.

cô ấy means she. In this sentence, it refers to An.

Vietnamese often uses pronouns instead of repeating a name, just like English. So:

• An đã chọn... vì cô ấy biết...
  = An chose... because she knew...

This helps the sentence sound more natural.

Also, An is a name that may not immediately tell a learner whether the person is male or female, so cô ấy makes it clear that An is female.

However, in some contexts, Vietnamese might also simply repeat the name:

• An đã chọn sách làm quà vì An biết Lan thích đọc.

That version is grammatically possible, but usually less natural here.

In this sentence, the most natural interpretation is that cô ấy refers to An, not Lan.

Why?

Because of sentence structure and logic:

• An đã chọn sách làm quà = An did the choosing
• vì cô ấy biết Lan thích đọc = the person who knew that Lan likes reading is most naturally An

So the idea is: An chose books as a gift because An knew Lan likes reading.

If a speaker wanted to avoid even a small chance of ambiguity, they could say:

• An đã chọn sách làm quà vì biết Lan thích đọc.

This is also very natural and removes the extra pronoun.

Vietnamese often does not need a word equivalent to English that in this kind of sentence.

So:

• biết Lan thích đọc = know that Lan likes reading

This is a very common pattern. Vietnamese often places the content of what is known, said, heard, etc. directly after the verb.

Examples:

• Tôi biết anh bận. = I know (that) you are busy.
• Cô ấy nói mai sẽ đến. = She said (that) she would come tomorrow.

Sometimes Vietnamese uses rằng for that, especially in more formal writing:

• Tôi biết rằng anh bận.

But in everyday speech, leaving it out is very common.

thích đọc means like reading.

Here:

• thích = like
• đọc = read

When no object follows đọc, it has a general meaning:

• Lan thích đọc = Lan likes reading

If you want to say what she likes to read, you can add an object:

• Lan thích đọc sách. = Lan likes reading books.
• Lan thích đọc truyện. = Lan likes reading stories/fiction.

So the sentence is not incomplete. It simply means Lan enjoys reading in general.

Here, biết means know.

So:

• cô ấy biết Lan thích đọc = she knew that Lan likes reading

In other contexts, biết can sometimes be translated in slightly different ways, such as find out, be aware, or know how to, but in this sentence the plain meaning is just know.

Examples:

• Tôi biết anh ấy. = I know him.
• Tôi biết chuyện đó. = I know about that.
• Tôi biết bơi. = I know how to swim.

Yes, both are possible depending on context.

1. Without đã:
   • An chọn sách làm quà vì cô ấy biết Lan thích đọc.

This can still be understood, especially if the context already makes the time clear.

2. Without cô ấy:
   • An đã chọn sách làm quà vì biết Lan thích đọc.

This is very natural in Vietnamese. The subject of biết is understood to be An.

Vietnamese often drops words that are clear from context, especially subjects and tense markers.

Yes. The sentence follows a very typical Vietnamese structure:

• An = subject
• đã chọn = past marker + verb
• sách = object
• làm quà = purpose/result-like phrase meaning as a gift
• vì... = reason clause

So the overall pattern is:

• Subject + time marker + verb + object + extra phrase + reason

A rough breakdown:

• An / đã chọn / sách / làm quà / vì cô ấy biết Lan thích đọc

This kind of order is very normal in Vietnamese.

Yes. A classifier such as cuốn could be used, especially if the speaker wants to emphasize that actual physical books are being chosen.

For example:

• An đã chọn một cuốn sách làm quà... = An chose a book as a gift...
• An đã chọn vài cuốn sách làm quà... = An chose a few books as a gift...

But in the original sentence, sách without a classifier is perfectly natural because it is being used in a general way.

Not necessarily from the name alone, especially for learners.

• Lan is very commonly female.
• An can be male or female depending on the person.

That is one reason why cô ấy is helpful here: it tells you that An is female.

In Vietnamese, names do not always work like English names, where learners may immediately recognize gender. So pronouns can provide useful clarification.