Have you ever learnt a modern foreign language? Many of us have attempted it at least once in our lives. Perhaps it was in school, or perhaps you fell in love. However, an encounter with a new language arises, starting to learn always seems easy. But how do you know when you have finished, or reached the target? At what point can you say you have acquired the language? Is it, perhaps, when you know all the rules in the grammar book? Or when you stop speaking with a foreign accent? The questions surrounding how much language is sufficient to have acquired it are ones that have been testing learner, teacher and researcher alike.