Today I wondered what two dots over a vowel means. (Besides the umlaut, I know that one). It’s called diaeresis and it’s something we should bring back. English is difficult enough as it is. And while people may not have trouble pronouncing words such as coöperate or naïve, every little bit helps.
So is it diaeresis or diaëresis? If you can pronounce it either way then does it not get one? It’s also called hiätus. FYI.