In historical linguistics, a chain shift is a set of sound changes in which the change in pronunciation of one speech sound (typically, a phoneme) is linked to, and presumably causes, a change in pronunciation of other sounds. The sounds involved in a chain shift can be ordered into a "chain" in such a way that after the change is complete, each phoneme ends up sounding like what the phoneme before it in the chain sounded like before the change. The changes making up a chain shift, interpreted as rules of phonology, are in what is termed counterfeeding order.
A well-known example is the Great Vowel Shift, which was a chain shift that affected all of the long vowels in Middle English. The changes to the front vowels may be summarized as follows:
: → → →
A drag chain or pull chain is a chain shift in which the phoneme at the "leading" edge of the chain changes first. In the example above, the chain shift would be a pull chain if changed to first, opening up a space at the position of , which then moved to fill. A push chain is a chain shift in which the phoneme at the "end" of the chain moves first: in this example, if moved toward , a "crowding" effect would be created and would thus move toward , and so forth.
Examples
During the Great Vowel Shift in the 15th and 16th centuries, all of the long vowels of Middle English, which correspond to tense vowels in Modern English, shifted pronunciation. The changes can be summarized as follows:
Nzebi (or Njebi), a Bantu language of Gabon, has the following chain shift, triggered morphophonologically by certain tense/aspect suffixes:
{|
| || → || || → || || → ||
|-
| || || || || || → ||
|-
| || || || → || || → ||
|}
Examples follow:
:{|
! Underlying form !! Chain-shifted form
|-
| "to work" || →
|-
| "to give" || →
|-
| "to carry" || →
|-
| "to refuse" || →
|-
| "to go down" || →
|-
| "to arrive" || →
|-
| "to hide oneself" || →
|}
Another example of a chain from Bedouin Hijazi Arabic involves vowel raising and deletion: