Grammaticalization within and outside of a domain

The emergence of many grammatical categories cannot be explained in terms of the semantic properties of the source and the target or in terms of other cognitively based processes or language use such as metaphor, metonymy, usage and frequency of use. The term ‘grammaticalization’ refers here to the emergence of grammatical systems. The specific aim of the present study is to demonstrate that a primary factor involved in grammaticalization is the human ability, most often unconscious, to analyse language, an activity that falls within Hagège’s concept of ‘language builder’. The study describes the grammaticalization of tone in several Chadic languages. The proposed addition to grammaticalization theory contributes to the understanding of the origin of binary distinctions in language.