gettextの Plural-Forms: ヘッダ

http://www.gnu.org/software/gettext/manual/gettext.html#PO-Files

The nplurals value must be a decimal number which specifies how many different plural forms exist for this language. The string following plural is an expression which is using the C language syntax. Exceptions are that no negative numbers are allowed, numbers must be decimal, and the only variable allowed is n. Spaces are allowed in the expression, but backslash-newlines are not; in the examples below the backslash-newlines are present for formatting purposes only. This expression will be evaluated whenever one of the functions ngettext, dngettext, or dcngettext is called. The numeric value passed to these functions is then substituted for all uses of the variable n in the expression. The resulting value then must be greater or equal to zero and smaller than the value given as the value of nplurals.

nplurals ってパターンの数なのね。。。単数形と複数形の２つしかなければ「２」ってことね。
で、plural の方がｃの形式で書けと。返す数は表示するmsgstrの[]内の数にしろと。。。
n が変数として使えてngettextとかで呼ばれたときに渡された数が渡されると。。。
思いっきり勘違いしてたわ。