Know cannot be followed directly by an infinitive. Instead we use the structure know how to.
- He knows how to operate a computer.
- She knows how to make pizza.
- He knows how to play the piano.
- Do you know how to make Spanish omelettes?
Know is one of those verbs which cannot be usually used in continuous forms.
- I know what you mean. (NOT I am knowing what you mean.)
Know can be used in the present perfect tense form.
- I have known her for a long time.
- We have known each other since our childhood.
Know can be followed by an object + infinitive in a very formal style.
- I knew him to be a generous guy.
In a less formal and more natural style, we use a that-clause.
- I knew that he was a generous guy.
- I always knew that I couldn’t depend upon him.
Expressions with know
Know one’s own mind: be certain of one’s purpose, ideas etc.
Know what’s what: have common sense, good judgment, practical experience etc.
In the know: having information not shared by all
- Those in the know don’t do things like that.
To the best of my knowledge: As far as I know
- The information that I have given is true to the best of my knowledge.