Playing on words, I propose to examine a very serious question: the way in which the two terms ‘mise en scène’ and ‘performance’ allow us, and also oblige us, to think about how a production is interpreted, and indeed about our very conception of theatre. The two languages, English and French, in fact see things very differently, and are more or less capable of describing the phenomenon of theatre as it constantly evolves. At various times in the history of the theatre, in particular over the twentieth century, words and concepts from different languages have been unevenly appropriated to capture changes in conception. At certain points, words cease to be appropriate, and we are likely to return to another linguistic and conceptual way of describing phenomena, switch languages, or even turn to neologisms.