you forgot "j, u" and the plural of Umlaut = Umlaute
The English language is easier, you mostly use "s" or variations ending with "s" - but the German language has more sadistic fantasies.
die Phantasie/Fantasie = haha, feminine(spelling reform) = plural -> die Phantasien/Fantasien
die Sprache = language, feminine (yeah, we're chatty) = Plural -> die Sprachen
die Katastrophe = catastrophy, feminine <img src="/ubbthreads/images/graemlins/delight.gif" alt="" /> = Plural -> die Katastrophen
der Laerm = noise, masculine <img src="/ubbthreads/images/graemlins/delight.gif" alt="" /> - no plural form existing there
so, as a very coarse rule you can say, words ending with "e" turn to "en" in Plural - but I'm sure, I can give you a lot of exceptions. As a rule to the German language, and very coarse here again = rules live due to exceptions. German is an exception(al) language <img src="/ubbthreads/images/graemlins/evilgrin1.gif" alt="" />
it would be normal to say, words ending with a consonant would simply get the plural ending "e" - nope.
die Kartoffel = potato, feminine = plural -> die Kartoffeln
der Flug = flight, masculine = plural -> die Fluege - pretty, ain't it?
Kiya