In history writing, we need to have words, whether technical or not, to denote economic tendencies, changes in institutions, exchanged objects, or social practices. These words may remain the same, but behind their stability, they designate specific historical configurations. In this concluding note, I reflect on the possible meaning of the words we currently use to describe the social and economic histories of Africa in the long era stretching from 300 to 900 CE (or even 1000, as the title of this collection argues). I draw particular attention to the word "transition" which in the contemporary literature has become an umbrella term to describe any kind of transformation occurring across time. The result of this intellectual operation is that any implication about historical periodization and "structural changes" has vanished from the research agenda. In outlining the contents of this collection, my crucial task here is to restore the potent analytical meaning that a word such as transition implies and to reject the tendency to transform the descriptive into the explanatory.