public function isPlural($word)
    {
        // Try the cache for an known inflection.
        $inflection = $this->getCachedSingular($word);

        if ($inflection !== false) {
            return true;
        }

        // Compute the inflection to cache the values, and compare.
        return $this->toPlural($this->toSingular($word)) == $word;
    }