Pronunciation and language change. First, attempt to pronounce the words that you find at the left-hand side. What do you notice?
If all has gone well, you will have noticed that while these words are written with a different vowel, the vowel is pronounced the same. Namely, as –eh. “Bury”, “friend”, “Geoffrey”, “leisure”– in British English– “says”, “sweater”, “Thames”, “better”. Now, pronounce the words at the right. What do you notice here?
Here we have exactly the opposite situation. The vowel in these words is written the same but pronounced differently. “Bone”, “done”, “gone”, “cord”, “word”, “womb”, “woman”, “women”. What we can conclude from this exercise is that there is no one-to-one correspondence between letters and sounds.
English is particularly notorious for such mismatches between spelling and pronunciation. English has many homophones, same pronunciation but different spelling, like “weight” and “wait”. Homographs, same spelling but different pronunciation, like the noun “conduct” /ˈkɒndʌkt/ and the verb “to conduct” /kənˈdʌkt/ . Words that start with a vowel letter but a consonant sound, as in “usual”. Words that have so-called silent letters, that is, letters that are not pronounced, as with the final consonant cluster in the word “through”. Words in which two letters are pronounced as one sound, as with the th– /θ/ in the same word, “through”, or the same consonant cluster in the different word, “enough”, –/f/, and so on and so forth.
For this reason, we cannot use letters to represent sounds. Instead, we use the phonetic symbols of the IPA, the International Phonetic Alphabet. Accordingly, all of the vowels in these words have a different phonetic symbol. You may ask why the system is so inconsistent. As a rule of thumb, you can assume that historically, all English words used to be pronounced in the way that they’re written. The inconsistency has arisen from, amongst other things, a number of language changes that have occurred in the history of English. One such language change– the so-called FOOT-STRUT split– took place in the 17th century.
As you can see from spelling, originally words like these three were pronounced with the same long vowel –/oː/. “mood” /moːd/, “foot” /foːt/, and “blood” /bloːd/. And words like these two were also pronounced with the same short vowel –/u/, /put/ and could /kud/.
The class of /oː/ words separated. In some words, like /moːd/, the long vowel came to be pronounced as a closer vowel by a process that has had a major impact on English pronunciation and is known as the Great Vowel Shift. Mood /muːd/. Most other words, like “foot” /foːt/ and “blood” /bloːd/ joined the short –/u/ class. Subsequently, the short –/u/ class split. In some words, the vowel was somewhat centralised to –/ʊ/. For example, “put” /pʊt/, “foot” /fʊt/, and other words developed a new vowel that linguists refer to as the STRUT-vowel. Thus, the vowel that we nowadays find in the words like “strut”, including “cut” /kʌt/ and “blood” /blʌd/, hence the name FOOT-STRUT split.
Some dialects of English, especially in the north of England, did not participate in the FOOT-STRUT split and never developed the STRUT-vowel. Speakers of those dialects, therefore, have one lexical set comprising “put”, “foot”, “strut”, and “cut”. Some languages other than English do not have the STRUT-vowel in their inventory of vowels either. If your native language is a STRUT-less language, I’d recommend you think of pronouncing the vowel –ah. “Straht”, “blahd”, and not, for example, “struht”, “blohd”, as you may be inclined to on the base of the way in which the vowel is written. If you look up the STRUT-vowel in the vowel diagram, you will see that its place is actually very close to the PALM-vowel /ɑɑh/.