In the study of phonetic changes, a chain shift is a type of sound shift in which a group of sounds all change at about the same time, with some sounds taking the place of others.
Examples of sound shifts that have occurred in English are the Great Vowel Shift in the 15th century, and the ongoing Northern cities vowel shift.
While a chain shift usually occurs as a set of vowel shifts, chain shifts can also occur in consonants. For example, a set of plosives that have a voiced / voiceless distinction may shift to have a aspirated / unaspirated distinction. In this case, the voiceless consonants become aspirated, and the voiced consonants become voiceless. A famous example of such a shift is the well-known Grimm's Law which turned the Proto-Indo-European voiceless/voiced/breathy-voiced distinction into a fricative/voiceless/voiced distinction.
