The Great Vowel Shift , or, Why English Spelling Makes No Sense Why does the English language have such weird spelling? Well, there was a time, around 600 years ago, when the spelling made a lot more sense than it does now. One main reason that this is no longer the case is the Great Vowel Shift. This was a major change in the way English vowels work, and it started in about 1400. There are various competing theories as to why this happened, some of which are based on population migrations following the Black Death. The diagram shows how English vowel sounds have moved around in the last 600 years. English has a rather complicated vowel system compared to, say, the five-vowel system of Spanish. The vowel system of Spanish has not changed very much in the last 600 years, but the relatively large number of distinct vowels in English means that as soon as one of the vowels starts to be pronounced slightly differently, there is a good chance that it will displace a nearby vowel and set a...