Tôi đã lầm.

• Tôi = I
• đã = a marker that often shows a completed action or a past-time sense
• lầm = to be mistaken / to be wrong / to make a mistake

So word-for-word, the sentence is roughly I already was mistaken or I was wrong.

Đã often marks something as completed or as belonging to the past.

In Tôi đã lầm, it tells you the speaker is talking about a mistake that has already happened. In natural English, you usually would not translate it literally as already every time. Instead, you would often just say:

• I was wrong.
• I was mistaken.

So đã adds a past/completed feeling, even if English expresses that more simply.

It behaves like a stative verb in Vietnamese.

Vietnamese often uses verbs where English might use to be + adjective. So instead of needing a separate word for was, Vietnamese can simply say:

• Tôi lầm = I am mistaken / I am wrong
• Tôi đã lầm = I was mistaken / I was wrong

So lầm is best understood as a verb meaning to be mistaken or to err.

Vietnamese does not need a verb like to be in many sentences where English does.

In English, you say:

• I was wrong.

In Vietnamese, you can simply say:

• Tôi đã lầm.

The tense or time reference is often shown by words like đã, đang, sẽ, or by context, rather than by changing the verb the way English does.

Yes, it is understandable and correct, but it sounds a bit literary, formal, or old-fashioned in everyday conversation.

In modern spoken Vietnamese, people are often more likely to say:

• Tôi nhầm rồi.
• Tôi sai rồi.
• Tôi đã sai.

So Tôi đã lầm is fine, but it may sound more serious, reflective, or written than casual daily speech.

These words are related, but they are not exactly the same.

• lầm = mistaken / in error
  Often a bit literary or formal. Example: Tôi đã lầm.

• nhầm = mistake/confuse/misidentify
  Very common in everyday speech. Example: Tôi nhầm rồi. = I was mistaken.

• sai = wrong / incorrect
  Very common and broad. Example: Tôi sai rồi. = I was wrong.

Very roughly:

• lầm often emphasizes being mistaken in judgment
• nhầm often emphasizes confusion or misidentification
• sai is the most general word for being wrong

Yes, you may hear or use rồi in similar situations, but Tôi lầm rồi is still less common than Tôi nhầm rồi or Tôi sai rồi.

Both đã and rồi can relate to completion, but they do not work exactly the same way:

• đã often marks past/completed action more neutrally
• rồi often emphasizes that something has happened or is now the case

For modern everyday speech, these are more natural:

• Tôi nhầm rồi.
• Tôi sai rồi.

Yes, if the context is clear.

Vietnamese often drops pronouns when they are understood. So in the right context, someone might simply say:

• Đã lầm rồi.
• Lầm rồi.
• Nhầm rồi.

However, as a full standalone learning example, Tôi đã lầm is clearer because it explicitly includes the subject.

No. You can say:

• Tôi lầm.
• Tôi đã lầm.

The difference is that đã makes the past/completed sense more explicit.

• Tôi lầm can sound more general or depend more on context
• Tôi đã lầm clearly points to a mistake that occurred

In real usage, Vietnamese often relies on context, so speakers do not always include time markers if the situation already makes the time clear.

Lầm is pronounced roughly like lum with a short vowel, but with a low falling tone.

A few pronunciation notes:

• l is like English l
• â is a short central vowel, somewhat like the vowel in English but, but shorter and not identical
• m is a normal m
• the grave accent (`) gives it the huyền tone, which is a low falling tone

So it sounds something like: lầm.

Usually it means admitting a mistake or admitting mistaken judgment, not necessarily moral guilt.

Depending on context, it can mean things like:

• I was wrong.
• I misjudged it.
• I was mistaken.

If you wanted to express stronger guilt or wrongdoing, Vietnamese would often use other words depending on the situation, such as sai, có lỗi, or more specific expressions.

It fits well in a reflective or serious context, especially when someone realizes their judgment was wrong. For example:

• Tôi đã lầm khi tin anh ấy.
  I was wrong to trust him.

• Tôi đã lầm về cô ấy.
  I was mistaken about her.

So the sentence works especially well when the speaker is reconsidering something and admitting they judged it incorrectly.