public static function plural(string $word) : string
    {
        // Check that `$word` is countable.
        if(in_array($word, Inflector::$_uncontable)) {
            return $word;
        }

        // Now check that `$word` is regular.
        if(isset(Inflector::$_plural["irregular"][$word])) {
            return Inflector::$_plural["irregular"][$word];
        }

        // Now check that `$word` can be pluralize.
        foreach(Inflector::$_plural["uninflected"] as $rule) {
            if(preg_match("/^". $rule ."$/", $word)) {
                return $word;
            }
        }

        // Now the word follows a rule, so apply it
        foreach(Inflector::$_plural["rules"] as $key => $value) {
            if(preg_match($key, $word)) {
                return preg_replace($key, $value, $word);
            }
        }

        // Well, right now the word couldn't be pluralized
        // so return it as it was (or throw an exception?)
        return $word;
    }