Nowadays, linguists do not question the existence of synchronic variation, and the dichotomy between synchrony and diachrony. They recognize that synchrony can be motivated regionally (diatopic variation), sociolinguistically (diastratic variation), or stylistically (diaphasic variation). But, further, they can also recognize the hybrid nature of synchrony, which is referred to as "dynamic synchrony." This conception of synchrony assumes that similar patterns of usage can coexist in a community during a certain period and that their mutual relations are not static but conflicting enough to result in a future systematic change through symptomatic synchronic variation. Emergence of a large corpus of written texts for some languages has enabled quantitative as well as qualitative analyses of the synchronic conditions for diachronic changes, over both long and short spans of time. Most of the 14 papers in this volume represent studies on synchronic and diachronic variations based on such corpus data.