Halliday & Matthiessen (2014: 68):
Nevertheless we can recognise grammaticalisation as a process taking place in time – in fact, in three distinct dimensions of time.(i) We can see it in ontogenetic time when we observe children’s early language development, which is built around the creation of proto-grammatical and then grammatical systems.
(ii) We cannot observe it directly in phylogenetic time, the evolution of human language; but we can track examples in the history of particular languages (for example, secondary tenses and the passive voice in English.
(iii) We can see it in logogenetic time, the unfolding of discourse, when a passage of some extent – a clause or more – is recapitulated in a single word or group.