# What is the difference between “a” and “per”?

1.The train runs 60 miles an hour. 2.The train runs 60 miles per hour. What is the differen between the two sentences.

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the first (an hour) is English wording and the second (per hour) is using Latin. What's the problem? – teylyn Mar 10 '14 at 9:27
Just my opinion, but maybe this could be migrated to English Language Learners, and the user might want to check out that sister Stack Exchange site. – J.R. Mar 10 '14 at 9:39

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.

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It's a bit different.

Per = pro(German) = for --> for each hour of running a train will cover a distance of 60km

vs

con = against

and

an hour = in an hour --> the train can cover a distance of 60km inside the timespan of an hour

Both are saying the same essentially. The one just focusses on if you have one hour only, how much distance can you cover in! that hour, while the first one talks about how much time or hours you would need in order for! you to travel a certain distance.

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In the context of this question, there is no difference between the meaning or connotation of "per" and "an". – MrHen Mar 18 '14 at 15:18
This "goof" in Back to the Future Part III mentions that a "true scientist" would know the difference between the two terms. I guess it relates to this? – Deanna Oct 26 '14 at 20:13