It will be argued that the constructions that express reciprocity in Present-day English are not distributed randomly, but rather form a system in which different forms compete with each other. (The details of this idea will be laid out in Chapter 5.) In Chapter 3 we will track how this system has developed in the history of English. To be sure, it would of course be misleading to claim that Present-day English has a regular system of expressing reciprocity, whereas the linguistic expression of such situations in older stages of English was unsystematic. At every stage of the language there was some kind of system of reciprocal constructions. Yet, from the point of view of grammatical constructions becoming more fi xed formally, on the one hand, and the number of different constructions being gradually reduced to a well-organized subset on the other, we can indeed observe a change. This change involves at least the following aspects: what will be called the ‘basic reciprocal construction’, the construction containing the expression each other/one another, emerges as a result of grammaticalization and lexicalization. Furthermore, the basic reciprocal construction does not become too specialized semantically and as a result interacts with the two other main types of reciprocal construction in such a way that in all contexts a functional differentiation is possible.