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: Most vowels shifted to a higher
place of articulation, so that the pronunciation of
geese changed from to and
broken from to . The high vowels and became
diphthongs (for example,
mice changed from to ), and the low back vowel was
fronted, causing
name to change from to . The Great Vowel Shift occurred over centuries, and not all
varieties of English were affected in the same ways. For example, some speakers in
Scotland still pronounce
house similarly to its sound in Middle English before the shift, as . A chain shift may affect only one
regional dialect of a language, or it may begin in a particular regional dialect and then expand beyond the region in which it originated. A number of recent regional chain shifts have occurred in English. Perhaps the most well known is the
Northern Cities Vowel Shift, which is largely confined to the "
Inland North" region of the United States. Other examples in North America are the
Pittsburgh Vowel Shift, the
Southern Vowel Shift (in the
Southern United States), and the
Low-Back-Merger Shift. In England, the
Cockney vowel shift among working-class Londoners is familiar from its prominence in plays such as
George Bernard Shaw's
Pygmalion (and the related musical
My Fair Lady): : → → → → Many chain shifts are
vowel shifts, because many sets of vowels are naturally arranged on a multi-value scale (e.g.
vowel height or frontness). However, chain shifts can also occur in consonants. A famous example of such a shift is the well-known First Germanic Sound Shift or
Grimm's Law, in which the
Proto-Indo-European voiceless stop consonants became
fricatives, the plain
voiced stops became voiceless, and the
breathy voiced stops became plain voiced: : → → → : → → → : → → → Another is the
High German consonant shift which separated
Old High German from other
West Germanic dialects (namely
Old English,
Old Frisian,
Old Saxon, and
Old Low Franconian). : Note that the rightmost development in the table is the oldest (drag chain). The degrees to which High German dialects have completed these changes vary vastly (see
Rhenish fan). The Romance languages to the north and west of central Italy (e.g.
French,
Spanish,
Portuguese,
Catalan and various northern Italian languages) are known for a set of chain shifts collectively termed
lenition, which affected
stop consonants between vowels: : → → → , : → → → (or vanishes) : → → → , (or vanishes) In this case, each sound became weaker (or more "lenited"). ==Synchronic shifts==