Hi,
We, the i18n team, are working on automated test cases for the plural forms for languages and we found support for fractional numbers is incomplete. Some languages have a separate plural form if the number is a fraction number.
For example, Russian language, according to CLDR[1] has 4 plural forms. They are:
'one' for 1, 21, 31, 41, 51, 61... 'few' for 2-4, 22-24, 32-34... 'many' for 0, 5-20, 25-30, 35-40... 'other' for 1.2, 2.07, 5.94...
Note the 'other' form, it is for fractional numbers. This bug: https://bugzilla.wikimedia.org/show_bug.cgi?id=28128 also lists a Polish language example. In the above Russian rules, Mediawiki as of now defines only 3 forms. So that is a bug as reported in Bug 28128.
If you can check the plural form definition for your language in CLDR using http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_ru... and check if Mediawiki implementation is correct for your language, it will be a great help to us.
CLDR plural forms may not be 100% correct, but there are ways to correct it. Mediawiki plural rules often fallback to the last form supplied using {{PLURAL...}} syntax, but that is not well tested. You can test the behavior of plural in your language by trying a test page with content like {{PLURAL:10.5|plural-form-1|plural-form-2|plural-form-n}} in your wiki. If you give correct number of forms as per your language, and if not getting the correct form with fraction numbers, let us know by reporting a bug in Mediawiki bugzilla[2].
[1] http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_ru... [2] https://bugzilla.wikimedia.org/
Thanks Santhosh Thottingal