Is there any algorithm in c# to singularize - pluralize a word?

Question

Is there any algorithm in c# to singularize - pluralize a word (in english) or does exist a .net library to do this (may be also in different languages)?

Answer 1

Most ORMs have a stab at it, although they generally aren't perfect. I know Castle has it's Inflector Class you can probably poke around. Doing it "perfectly" isn't an easy task though (English "rules" aren't really rules :)), so it depends if you are happy with a "reasonable guess" approach.

Answer 2

As the question was for C#, here is a nice variation on Software Monkey's solution (again a bit of a "cheat", but for me really the most practical and reusable way of doing this):

    public static string Pluralize(this string singularForm, int howMany)
    {
        return singularForm.Pluralize(howMany, singularForm + "s");
    }

    public static string Pluralize(this string singularForm, int howMany, string pluralForm)
    {
        return howMany == 1 ? singularForm : pluralForm;
    }

The usage is as follows:

"Item".Pluralize(1) = "Item"
"Item".Pluralize(2) = "Items"

"Person".Pluralize(1, "People") = "Person"
"Person".Pluralize(2, "People") = "People"

Answer 3

Subsonic 3 has an Inflector class which impressed me by turning Person into People. I peeked at the source and found it naturally cheats a little with a hardcoded list but that's really the only way of doing it in English and how humans do it - we remember the singular and plural of each word and don't just apply a rule. As there's not masculine/feminine(/neutral) to add to the mix it's a lot simpler.

Here's a snippet:

AddSingularRule("^(ox)en", "$1");
AddSingularRule("(vert|ind)ices$", "$1ex");
AddSingularRule("(matr)ices$", "$1ix");
AddSingularRule("(quiz)zes$", "$1");

AddIrregularRule("person", "people");
AddIrregularRule("man", "men");
AddIrregularRule("child", "children");
AddIrregularRule("sex", "sexes");
AddIrregularRule("tax", "taxes");
AddIrregularRule("move", "moves");

AddUnknownCountRule("equipment");

It accounts for some words not having plural equivalents, like the equipment example. As you can probably tell it does a simple Regex replace using $1.

Update:
It appears Subsonic's Inflector is infact the Castle ActiveRecord Inflector class!

Answer 4

You also have the System.Data.Entity.Design.PluralizationServices.PluralizationService.

UPDATE: Old answer deserves update. There's now also Humanizer: https://github.com/MehdiK/Humanizer

Answer 5

Not much documentation from MSDN on the specific usage of the PluralizationService class so here is a unit test class (NUnit) to show basic usage. Notice the odd test case at the bottom that shows the service isn't perfect when it comes to non-standard plural forms.

[TestFixture]
public class PluralizationServiceTests
{
    [Test]
    public void Test01()
    {
        var service = PluralizationService.CreateService(CultureInfo.CurrentCulture);

        Assert.AreEqual("tigers", service.Pluralize("tiger"));
        Assert.AreEqual("processes", service.Pluralize("process"));
        Assert.AreEqual("fungi", service.Pluralize("fungus"));

        Assert.AreNotEqual("syllabi", service.Pluralize("syllabus")); // wrong pluralization
    }
}

Answer 6

I can do it for Esperanto, with no special cases!

string plural(string noun) { return noun + "j"; }

For English, it would be useful to become familiar with the rules for Regular Plurals of Nouns, as well as Irregular Plurals of Nouns. There is a whole Wikipedia article on the English plural, which may have some helpful information too.