Would you explain the difference between the following?

I know of somebody/something.
I know about somebody/something.


2 Answers 2


Yep. This is the best example:

  1. I know of atomic physics (I have heard the name, but that is about all I know.)

    When you say know of someone/something, it means to know that someone or something exists but don't know very well.

  2. I know about atomic physics (I have learned this subject and can do the calculations.)

    When you say know about someone/something, it means to know that someone or something exists and you know very well that thing/person.

  • Thanks. Nevertheless, do you use them interchangeably?
    – nima
    Aug 7, 2014 at 15:19
  • 1
    I do not consider them interchangeable. If I say "I know Bob.", I mean that I regard Bob as an acquaintance or friend. I've met him, and he probably knows who I am. If I say "I know of Bob", I just mean that I've heard of him. He might be a politician whose policies I'm aware of, or an artist whose work I enjoy, but it doesn't imply that I've actually met him or that he knows who I am. Aug 7, 2014 at 15:39
  • 3
    I agree. I do not use them interchangeably. Often, I say, "I know of it" when I want to emphasize that I don't know very much. For example, if someone asks, "Do you know about the Battle of Lepanto?" I might answer "I know of it," in order to emphasize that I don't know very much. Aug 7, 2014 at 18:09
  • 1
    To "know of" something is similar to "having heard of" something - it communicates that you recognize the term being used to reference a subject, but indicates nothing about the extent of your familiarity with the subject - it just, due to this, tends to be used in situations where there is little familiarity.
    – Pockets
    Aug 8, 2014 at 23:23

My interpretation of a few variations:

I know of The Spanish Inquisition.

I know of Richard.

I've heard of it/him. I am aware that it/he exists. But really the only thing I know about it/him is its/his name. When speaking aloud, typically the "of" gets emphasized.

I know about Astronomy.

I would not typically say this, as I think it doesn't carry any meaning. If I did say it, the next question would just be "How much do you know about it?" Better to come right out and say "I know a lot about Astronomy" or "I know a little about Astronomy" or some variation.

I know about Susan.

Implies that there is some specific knowledge about Susan that is known to you. If you have a daughter named Susan, and were hiding that fact, someone could say to you "I know about Susan".

I know Frank.

This means at least: I would recognize him if I saw him; I've interacted with him before; he is an acquaintance. But it does not exclude the possibility that you are relatives or good friends or lovers or anything else.

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