Choir looks surprising because English spelling is not a perfect map of modern pronunciation. Many spellings reflect a word’s history, not just the way it sounds today.
The word came into English through other languages, and its spelling kept traces of that journey. At the same time, English pronunciation changed over centuries. When sound changes happen but spelling stays more fixed, words can end up looking very different from how they are said.
This is why the letters ch do not always sound the same in English. Their pronunciation depends on the word’s origin and history.
- choir, the ch sounds like kw
- machine, the ch sounds like sh
- cheese, the ch sounds like the usual ch sound
So choir is not a random exception. It is a good example of how English keeps older spelling patterns even after pronunciation moves on. The result can look strange, but it also preserves clues about where a word came from.