Not

[HumbertoDeOz]

I was trying to make a definition of dull and then I got this problem that I know I've had before

I know I should say : To be sharp
but then to say the opposite how should I say?

To not be sharp
Not to be sharp
To be not sharp

[HumbertoDeOz]

I also know I could just say "Not sharp" my problem is saying:

To not be
Not to be...
Or whatever

[TutorBrian]

I think "Not sharp" is best. http://dictionary.reference.com/browse/dull

If you have to go the other route, I think "not to be sharp" is best. I'm thinking of the famous quote by Shakespeare: "To be or not to be: that is the question"

I could be wrong, can another tutor share?
_________________
Private lessons with Brian -Skype English Lesson

[HumbertoDeOz]

hahah man. That's a good example. to be or not to be. I'll take that, thanks!

[Beeesneees]

I'd use 'Not to be sharp', though strictly speaking:

to be sharp / to be not sharp
is more accurate.

Where possible, just 'sharp' and 'not sharp' would be better.

Of course, depending on the meaning of sharp, these antonyms would be better still:

It is sharp / it is blunt / it is dull
He is sharp / he is dull / he is slow
The suit is sharp / the suit is unfashionable
_________________
Cheers m' dears!