Why is there such a mismatch between the sounds represented by the vowel letters in English versus virtually every other language that uses the Latin alphabet? For instance, “oo” makes the /uː/ sound that rightfully belongs to the letter U. “ee” and “ea” make the /i:/ sound that is normally written I, and “a” can either be the expected /ɑ/ or the unusual /eɪ/.
Contrast this with a language like Spanish, where the symbols A E I O U represent the sounds “ah” “eh” “ee” “oh” “oo,” with the letters and their values inherited from Latin. Other European languages have more complex vowel inventories, but at least the most fundamental values of the vowel letters — sometimes called the “continental” values — tend to be preserved.
Why don’t we spell “eye” ai, “food” fuud, or “treaty” triti? The explanation depends on something called the Great Vowel Shift.
Introduced by Danish linguist Otto Jespersen in the early 20th century, the GVS refers to the wholesale restructuring of the long vowels that occurred roughly 1300-1700, between the times of Chaucer and Shakespeare. This transformation has often been considered the defining boundary between Middle English and Modern English.
Jespersen noted that the long vowels of Middle English underwent a series of changes that did not seem at all arbitrary or unconnected. He produced the following diagram to describe the pattern:
Jespersen’s diagram (1909)
The series on the left shows what happened to the front long vowels: Each vowel raised, taking the place of the next one in the series. The highest vowel /i:/, with no further room to raise (if the tongue went any higher it would hit the palate), was then “pushed out” and formed the diphthong /ei/ which today is the long I /aj/. This hypothesized process is known as a chain shift: one sound change triggers a restructuring of the entire system because speakers tend to avoid mergers that compromise intelligibility.
Similarly, a parallel set of changes occurred in the back long vowels: Each vowel raised one step, until the highest one /u:/ was “pushed out” and formed the diphthong /ou/.
While the sounds changed, our spellings are still based on the pre-shift system. You can get a better sense for how the spelling of long vowels in Middle English worked from this video of Chaucer’s Canterbury Tales read aloud.
We can also summarize the shift using a table of the Middle English long vowels and their present-day equivalents (adapted from Wikipedia):
| Word | Originally sounded like | Middle English vowel | Modern vowel |
| bite | “beet” | /iː/ | /aɪ/ |
| meet | “mate” | /eɪ/ | /iː/ |
| meat | “met” | /ɛ:/ | /iː/ |
| mate | “maht” | /ɑː/ | /eɪ/ |
| out | “oot” | /uː/ | /aʊ/ |
| boot | “bote” | /oʊ/ | /uː/ |
| boat | “bot” | /ɔː/ | /oʊ/ |
(interestingly, the contemporary “ah” sound as in “father” is a post-shift innovation that filled the empty space left by the lack of a low vowel).
One of the most remarkable things about linguistics is how organized abstract patterns emerge from tacit, unintentional, embodied processes that are distributed over time and space. Jespersen’s neat diagram summarizes the systematic differences between “Middle English” and “Modern English.” But of course, there was not just one Middle English but rather a vast array of highly divergent dialects. Nor is there agreement among speakers of Modern English on vowel sounds. And we know from textual, historical and linguistic analysis that the vowel changes took place over a span of hundreds of years.
In the 1980s, Stockwell and Minkova introduced an analysis that deconstructed this long-standing standard model. They show that the “chain shift” story only applies at best to the higher vowels /e/, /i/, /o/, and /u/, whereas the other changes in the lower vowels (in the shaded boxes) occurred several generations later, at different times in different dialects, and rather than being involved in a chain shift, caused mergers with vowels occurring in other contexts. What appears from afar as a unified series of changes turns out to be the accumulation of centuries of sound change, only parts of which are structurally connected.
Stockwell’s diagram (2002)
Matthew Giancarlo (2001) presents a fascinating and readable discussion of the history of the Great Vowel Shift as a concept, showing how Jespersen and his colleagues constructed a unified, linear conception of the English language as a single object developing over time towards the higher and more rational condition of Modern English, and how this conceptualization allowed for the packaging of a more complex, pluralistic history into the textbook story that all students of the history of the English language are familiar with.
In many ways this debate about the concept of the GVS reflects the eternal debate between the lumpers and the splitters, the modelers and the descriptivists, the abstract versus the concrete. It might be beyond our ability to understand what really happened; certainly the truth is too intricate to represent in a diagram with a handful of letters and arrows. Perhaps the GVS is a helpful abstraction, a useful fiction; but then again maybe it is misleading, harmful, even, as Giancarlo argues, perpetuating traces of nationalistic and colonial ideologies. Perhaps it is all those things at once.