To save others like me the trip to wikipedia, here's a snippet of wikipedia that explains what saagarjha is alluding to: [Diaereses are] now far less commonly

To save others like me the trip to wikipedia, here's a snippet of wikipedia that explains what saagarjha is alluding to: [Diaereses are] now far less commonly used in words such as coöperate and reënter except in a very few publications—notably The New Yorker [..]