According to the neogrammarians and de Saussure, all linguistic change is either sound change, analogy, or borrowing.1 Meillet (1912) identified a class of changes that don't fit into any of these three categories. Like analogical changes, they are endogenous innovations directly affecting morphology and syntax, but unlike analogical changes, they are not based on any pre-existing patterns in the language. Meillet proposed that they represent a fourth type of change, which he called GRAMMATICALIZATION. Its essential property for him was that it gives rise to new grammatical categories -that is, to categories previously unexpressed in the language -and thereby transforms its overall system. ". . . Tandis que l'analogie peut renouveler le détail des formes, mais laisse le plus souvent intact le plan d'ensemble du système grammatical, la "grammaticalisation"de certains mots crée des formes neuves, introduit des categories qui n'avaient pas d'expression linguistique, transforme l'ensemble du système."The "newness" of a category can be either a matter of content, as when a language acquires a new tense category, or a matter of new form for old content, as when postpositions turn into case 1 endings, or word order replaces morphology as the mark of grammatical relations. Meillet's generalizations are empirical rather than definitional, so they demand an explanation.He suggested that grammaticalization is due to the loss and renewal of expressiveness of speech forms in the use of language, reasoning that, since this is a constant factor in in the ordinary use of language, the changes it triggers must have an intrinsic direction. As for phonological weakening, he saw it as a consequence of the fact that function words (mots accessoires) ordinarily do not carry focus. Therefore, when a lexical item becomes a function word, speakers can afford to give it a reduced articulation, which then can become established as its normal pronunciation: