Never could understand why the French insisted on Le havre unless it had sexual connotations?
Or the pond = l'étang is plural (I think, I am not sure about that).
A url
http://www.edufind.com/english/grammar/Determiners3.cfm
Another one
http://www.usingenglish.com/glossary/indefinite-article.html
and another
http://www.geocities.com/sohlhaut/articles.html
Don't try it in French. They are sexist.
Consonents and 'y' but not unaspirated 'h's are proceeded by 'a', if that is the way they are pronounced. Otherwise it is an 'an'.
My interpretation (there might be exceptions?)
---------------------------------------------------------
aspirate | asp()rt | a. & n. M16. [L aspiratus pa...