So it is. Rather like how the English word order rules are particularly difficult, e.g. look at the weird table in <a href="http:&#x2F;&#x2F;grammar.ccc.commnet.edu&#x2F;grammar&#x2F;adjectives.htm" rel="nofollow">http:&#x2F;&#x2F;grammar.ccc.commnet.edu&#x2F;grammar&#x2F;adjectives.htm</a>, or German plurals.<p>Most children learn their native language(s) properly at about the same age, which suggests that the languages are comparably difficult to learn, and perhaps that if a language takes too long, it&#x27;ll be simplified. But there&#x27;s nothing that pushes languages to have the <i>same</i> difficulties.