Tôi ghi địa chỉ.

• Tôi = I
• ghi = write down, note, or record
• địa chỉ = address

So the sentence is built very simply as subject + verb + object.

Yes. Vietnamese here uses the same basic order as English:

• Tôi = subject
• ghi = verb
• địa chỉ = object

So it follows I + write down + the address.

Vietnamese usually does not use articles like the, a, or an the way English does.
Whether địa chỉ means an address, the address, or just address depends on context.

So Tôi ghi địa chỉ could be understood as:

• I write down the address
• I write down an address
• I note the address

The situation tells you which one is meant.

This is a very common question.

• viết usually means to write in a general sense
• ghi often means to write down, to note, to record

So ghi địa chỉ suggests noting down an address, such as copying it so you do not forget it.

Compare:

• Tôi viết thư. = I write a letter.
• Tôi ghi số điện thoại. = I write down a phone number.

In many situations, ghi sounds more natural than viết for short information like addresses, names, or numbers.

A rough guide:

• địa sounds somewhat like dee-uh or zee-uh depending on accent, but with Vietnamese vowel quality and tone
• chỉ sounds a bit like chee, but again with the correct Vietnamese vowel and tone

The tones matter:

• địa has a falling-glottal type tone in standard northern pronunciation
• chỉ has a dipping-rising tone in standard northern pronunciation

If you are just starting, focus on saying the two syllables clearly:

• địa
• chỉ

Also remember:

• đ is not the same as English d
• ch in chỉ is like ch in cheese

It is one expression meaning address.

Historically and structurally:

• địa relates to place/land/location
• chỉ relates to pointing/indicating

But in modern Vietnamese, learners should treat địa chỉ as a fixed vocabulary item meaning address.

Yes, sometimes. Vietnamese often drops pronouns when the subject is already clear from context.

For example:

• Ghi địa chỉ đi. = Write down the address.
• Đang ghi địa chỉ. = I’m writing down the address / Writing down the address.

But if you want a complete, neutral sentence for study, Tôi ghi địa chỉ is perfectly fine.

By itself, địa chỉ most often means a physical address, such as a home or business address.

But with extra words, it can also refer to other kinds of addresses:

• địa chỉ email = email address
• địa chỉ web = web address

So the base word is broad, but context usually tells you what kind of address it is.

Vietnamese verbs do not change form the way English verbs do, so the sentence can be interpreted in different time frames depending on context.

Tôi ghi địa chỉ could mean:

• I write down the address
• I am writing down the address
• I wrote down the address
  if the surrounding context makes that clear

If you want to make the ongoing action clearer, you can say:

• Tôi đang ghi địa chỉ. = I am writing down the address.

Yes, it is grammatical and natural, especially as a simple example sentence.

In real conversation, people might also say:

• Tôi ghi lại địa chỉ. = I write down the address / I note the address down.
• Tôi đang ghi địa chỉ. = I’m writing down the address.
• Cho tôi ghi địa chỉ nhé. = Let me write down the address.

So your sentence is good, but real speech often adds particles or context.

lại often adds the sense of again or down for later reference, depending on context.

So:

• ghi địa chỉ = write down the address
• ghi lại địa chỉ = write the address down, note the address down, or write it down so you have it

In many everyday situations, ghi lại sounds a little more complete or natural, especially when someone is taking note of information to remember it later.