Is there a Name for the Change of Vowels in German (Umlaute but also Contractions)?

Question

I often found the change of sounds (vowel to Umlaut or contractions in general, like from the sound ei to ie) of certain irregular verbs, or plurals hard to remember. Also, sometimes I got confused with change of vowels between words and adjectives with the same root.

I would like to know if is there a principle (I am sure there must be some sort of logic or historical reason) behind them. Like in the following examples:

• Fahrrad ↔ Fahrräder [plural of noun]
• fahren ↔ fährt [declension of verb]
• Stand ↔ ständig [adjective from noun within the same root]
• Stand ↔ Ständer
• unterscheiden ↔ Unterschied
• entscheiden ↔ entschieden [past participle]
• Farbe ↔ Färbung [another change in the vowel from that is hard to understand for me. In a way it is having the same root, but that could be questionable.]

Is there one or more general rules I could check to understand the logic behind them to not get confused?

Answer 1

There are two distinct phenomenons at work here: umlaut and ablaut.

Umlaut, sometimes also called i-mutation, is specific to Germanic languages. Germanic umlaut

The following vowel changes are umlauts:

• Fahrrad ↔ Fahrräder
• fahren ↔ fährt
• Stand ↔ ständig
• Stand ↔ Ständer
• Farbe ↔ Färbung

In German, umlaut can be easily recognized because it affects the pairs a/ä, o/ö, u/ü, and au/äu.

But umlauts also can be found in English, although much more rarely, for example: man/men.

Another vowel change is ablaut, which originates in Proto-Indo-European.

The following vowel changes are ablauts:

• unterscheiden ↔ Unterschied
• entscheiden ↔ entschieden

Ablauts can also be found in English irregular verbs, for example: to swim, swam, swum. But they also can be found in other Indo-European languages, such as Latin and Old Greek. Indo-European ablaut

In German, ablaut is almost exclusively found in irregular verbs, much like in English. The verbs with ablaut are called strong verbs. Germanic had a fairly regular system of 7 classes of strong verbs. This system has become more complicated and more irregular over time, so today I think there is no alternative to memorizing the forms of strong verbs.