What is the difference between "a" and "per" in "miles an/per hour? [closed]
1.The train runs 60 miles an hour. 2.The train runs 60 miles per hour. What is the differen between the two sentences.
They have the same denotation, as you'll find in a dictionary, but "a/an" sounds a bit colloquial to me. Although I often hear and say "a/an", I would only write (and normally see written) "per", except in very informal circumstances.