The definitions from the dictionary are very incomplete because friendship is not only the condition of sharing a friendly relationship and the feeling and behaviour that exists between friends. It is more than that.
In our point of view the word friendship has 2 meanings, one meaning is the good relationship that 2 or more friends have. For example, the good relationship that all the boys in the class have.
The other meaning of friendship is the secret and big problems that two real friends share without sharing that to anyone else, for example, the secrets that Gonza says to me.
Finally, friendship is the best noun that exists in my opinion. I think, that friendship is not only a noun, it is also a feeling.