This monograph is not primarily concerned with any of the special problems that occur when translating (translation as a literary art, as a problem in computer-programming, …) but is concerned with the analysis of what translation is. It sets up a theory of translation which may be drawn upon in any discussion of particular translation problems. The analysis and description of translation processes must draw upon a theory of language: a general linguistic theory. The author feels that language teachers may find the book of interest: the extent to which translation can be used in language teaching is an issue of great concern to teachers, one which cannot be discussed without the support of some theory about what translation is, about the nature of translation equivalence, the difference between translation equivalence and formal correspondence, the levels of language at which translations may be performed.