Use of "a" and "an" in English speech.
Love DuoLingo. New to it, but noticed on the website "hector mastered a English skill". Just thought I'd question this "modern" usage. I suspect it is becoming more common through non-vocalised on-screen communication. But if spoken English is being taught, "an English skill" would seem to me to be much better English. More skilful! :) Cheers.