The American convention is simple: stick to the singular. British English convention can be more complex: http://en.wikipedia.org/wiki/English_plural#Singulars_

The American convention is simple: stick to the singular. British English convention can be more complex: http://en.wikipedia.org/wiki/English_plural#Singulars_with_collective_meaning_treated_as_plural http://en.wikipedia.org/wiki/English_plural#Singulars_with_c...