Java API for plural forms of English words

Check Evo Inflector which implements English pluralization algorithm based on Damian Conway paper "An Algorithmic Approach to English Pluralization". The library is tested against data from Wiktionary and reports 100% success rate for 1000 most used English words and 70% success rate for all the words listed in Wiktionary.

If you want even more accuracy you can take Wiktionary dump and parse it to create the database of singular to plural mappings. Take into account that due to the open nature of Wiktionary some data there might by incorrect.

Example Usage:

English.plural("Facility", 1)); // == "Facility"
English.plural("Facility", 2)); // == "Facilities"

jibx-tools provides a convenient pluralizer/depluralizer.

Groovy test:

NameConverter nameTools = new DefaultNameConverter();
assert nameTools.depluralize("apples") == "apple"
nameTools.pluralize("apple") == "apples"

I know there is simple pluralize() function in Ruby on Rails, maybe you could get that through JRuby. The problem really isn't easy, I saw pages of rules on how to pluralize and it wasn't even complete. Some rules are not algorithmic - they depend on stem origin etc. which isn't easily obtained. So you have to decide how perfect you want to be.

considering java, have a look at modeshapes Inflector-Class as member of the package org.modeshape.common.text. Or google for "inflector" and "randall hauch".

Its hard to find this kind of API. rather you need to find out some websservice which can serve your purpose. Check this. I am not sure if this can help you.. (I tried to put word cacti and got cactus somewhere in the response).