Plural forms

KDE and Gettext can handle plural forms. If your language only has two 
plural forms thus matching English then your task is relatively easy.
However 1 or more than two plurals can cause a few problems.

Issues with plurals

Many progerammers speak English and therefore have never had to face the 
fact that some languages have more than one plural form.  They cannot
undersand why a phrase such as:
"Open %n file(s)" mikght be problematic.  Just adding s to a word makes
plurals in English easyb but other languages have much more compelx rules.
You will also encounter situations where a programmer places text such as 
this: "Not called for n=1" which creates a lot of conusion.  In english it
makes sense:
0 files
1 file
2 files
3 files

So indeed if it is not called for 1 you could provide a translation that 
looked like this:
msgstr "\n" # remember not called for N=1
"%n files"

However if you language has 4 plural forms then you would probably still 
need to define them all because you might find that n=1 is never called but 
n=101 might be called.

If you see issues like this report it to the programmer and try to explain the
pain that this causes.

What does a plural look like?

There are two styles of plural: KDE and Gettext - they look as follows:

KDE:
msgid "_n: Singular\n"
"Plural"
msgstr "Form 1\n"
"Forma 2"
"Form 3"

Gettext:
msgid "Singular"
msgid_plural "Plural"
msgtr[0] "Form 1"
msgtr[1] "Form 2"
msgtr[2] "Form 3"

Variable

Explanation of the difference between %n and other vars