As emotion and feeling, everyone knows the meaning of friendship. From Aristoteles to social scientists, seeking to understand it under the aspects of the Anthropology of Emotions, the relationship between people united by this feeling seems to have not been modified over the centuries. With the internet, friendship received the support of tools for computer-mediated communication, allowing friends to stay in touch more often, exchanging and sharing, chatting. Facebook, one of these tools, is a social network site that connect friends. In the space of social interaction this site has became, friends reproduce the codes of the relationship existing outside the social network online. What are these codes and how they are played online, as offline: these are the points on which this research intends to move forward. These codes make up the grammar of friendship, analyzed here from computer mediated communication, through Facebook, and the interactional pre-existing context to the emergence of this social networking site.