Singular or plural for enumerations?

Question

Here it is straight from Microsoft:

http://msdn.microsoft.com/en-us/library/4x252001(VS.71).aspx

Use a singular name for most Enum types, but use a plural name for Enum types that are bit fields.

One recommendation comes from the .NET Framework Design Guidelines, page 59-60:

Do use a singular type name for an enumeration, unless its values are bit fields.

public enum ConsoleColor {
  Black,
  Blue,
  Cyan,
  ...

Do use a plural type name for an enumeration with bit fields as values, also called a flags enum.

[Flags]
public enum ConsoleModifiers {
  Alt,
  Control,
  Shift
}

In the .NET Framework, most "normal" enums (e.g. DayOfWeek) have singular names and flag enums (e.g. StringSplitOptions, BindingFlags) have plural names. It makes sense, since a value of a flag enum can represent multiple items but for a non-flag enum, it can only represent a single item.

In general, I consider an enum definition to be a type definition, with the values of the enum being the different values the type can have; therefore it gets a singular name: enum Weekday { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY }; enum CoffeeSize { SMALL, MEDIUM, LARGE };

Yes. If you do the mental experience of implementing the enums as classes, then the fact that you'd use a singular name for the type should reveal that it makes sense to use singular names for such enums . E.g.,

struct Weekday {};

const Weekday SUNDAY;
const Weekday MONDAY;
const Weekday TUESDAY;

...

void func (Weekday *day)
{
   if (day == &SUNDAY)
       ...
}

For who prefers plurals in enums, would you name that struct Weekdays?

In general, I consider an enum definition to be a type definition, with the values of the enum being the different values the type can have; therefore it gets a singular name:

enum Weekday { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY };

enum CoffeeSize { SMALL, MEDIUM, LARGE };

Microsoft recommends using a singular name for enumerations unless it uses the Flags attribute. And as taken from the Framework Design Guidelines book you should not suffix enumeration type names with Enum, Flags, etc. and you should not prefix enumeration values with an abbreviation or acronym as was common with VB enumerations back in the day.