we covered this long, long ago (a year? ) and i think we agreed that ligiture was the printers term. you can also use a ligiture for the cross bars of a double ff as in griffin, or for a double tt as in batter. so ligitures are not quite the same thing as diphthongs. (this font does a ligiture for F but not for T--oops yes it does when bold.. but not plain. tt.)

and why is Ę not one? Ętna is not a long A sound (etna)-- (butĘsops is A-sops.). so is ę a diphthohg some of the time?