Wordnet: Let you go up&#x2F;down the hierarchy and to siblings.<p><a href="http:&#x2F;&#x2F;wordnetweb.princeton.edu&#x2F;perl&#x2F;webwn?s=cosmos" rel="nofollow">http:&#x2F;&#x2F;wordnetweb.princeton.edu&#x2F;perl&#x2F;webwn?s=cosmos</a>