How can language change be measured?

Language change can be observed at various linguistic levels. A language’s vocabulary changes quite rapidly. New things and developments require new terms, whilst new perspectives lead to the replacement of existing terms. For example, "Krankenschwester" has become "Pflegefachfrau". Or young people set themselves apart from the older generation by using different terms for the same things than their parents do.

As a rule, sound change takes place at a slower pace. One example of this is consonant shifts in German, though not all regions have undergone them. This is why, in the northern regions’ dialects, people say “Appel”, whereas further south – and also in the standard language – they say “Apfel”. Linguistic change proceeds most slowly in morphology and syntax.

Both comparative linguistics and linguistic typology have developed various methods to identify similarities and differences between two language systems. For systematic comparisons, texts from different historical periods can be used; for example, the ‘Lord’s Prayer’, which has been handed down in numerous languages and at various stages of linguistic development.

How, then, can one assess the transition from one language to another? From a linguistic perspective, the transition from Old High German to Middle High German, to Early New High German and on to New High German, for example, always constitutes a continuum – that is, a series of varieties between which differences gradually emerge from generation to generation.

The fact that the names given to these languages change stems from conceptual frameworks in the history of language that suggest a break (Old High German up to this point, Middle High German from then on), which in reality never occurred.

For studies of changes in the spoken language in more recent times, it may be worthwhile to interview informants from different generations. The methodology for doing so can be found in the specialist literature on dialectology.