Those two dots, often mistaken for an umlaut, are actually a diaeresis (pronounced “die heiresses”; it’s from the Greek for “divide”). The difference is that an umlaut is a German thing ...

A diaeresis (also spelled “dieresis”) is a diacritical mark in the form of two dots, like an umlaut, placed over a vowel to indicate that it is pronounced as a separate syllable. I'm looking ...