When can I say I'm familiar?

[Hussein Baghdadi]

Hey,
These days I'm studying Python and Clojure programming languages.
If I digest the language core concepts (like control statements, data types, list comprehension and other idioms, you know), can I say that I'm familiar with the language? Can I be productive with it?
Some times I don't feel this is enough, sometimes I feel I have to build projects in order to be familiar with the language
What do you think?

[Jesper de Jong]

There is ofcourse no very clear and fixed definition of what "familiar" means - there is no clear criterium which you can use to measure if you are "familiar" with a certain programming language.

[Ulf Dittmer]

I wouldn't say that I'm familiar with any programming language that I haven't used for at least several programs. Just reading about it doesn't give a good feel for how it works, IMO.

[Marc Peabody]

I say I'm familiar when I feel confident I could hop on a new project with and be running full-steam in under two weeks.