ngettext() returns correct plural form of message
identified by msgid1 and msgid2
for count n. Some languages have more than one form
for plural messages dependent on the count.
<?php
setlocale(LC_ALL, 'cs_CZ');
printf(ngettext("%d window", "%d windows", 1), 1); // 1 okno
printf(ngettext("%d window", "%d windows", 2), 2); // 2 okna
printf(ngettext("%d window", "%d windows", 5), 5); // 5 oken
?>