Style Counsel

The dice is cast

Dice (noun). The small cubes with six faces bearing one to six dots, commonly used in games of chance. The use of dice as singular strikes one's ear as incorrect (mine, at least), but this usage has been common since the 14th century. Die seems to be the preferred singular in US English, whereas speakers of Australian and British English choose to use it as both singular and plural, with many an edited text using dice as singular. Editors of primary school books in particular choose the singular dice so as not to confuse the kids.

While Macquarie offers die as the singular of dice, it also notes that die is now rarely used, dice being the usual form for both singular and plural. One would therefore reason that dice is perfectly acceptable as the singular form of dice.