At the age of 65 I learned about the diaeresis. Used in such words as coöperate and naïve. Who knew?
Most consider it obsolete btw. Found it in a Bill McKibben article which doesn’t surprise me. Knew Bill briefly growing up and I’m proud to say I beat him at 1st affirmative defense in our very first debate on the Lexington High School debate team. After that it was downhill for me and good lord, look at Bill. A great and early voice on climate change.