You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <namespaces>
      <ns id="-2" case="first-letter" canonical="Media" xml:space="preserve">Ortam</ns>
      <ns id="-1" case="first-letter" canonical="Special" xml:space="preserve">Özel</ns>
      <ns id="0" case="first-letter" content="" xml:space="preserve" />
      <ns id="1" case="first-letter" subpages="" canonical="Talk" xml:space="preserve">Tartışma</ns>
      <ns id="2" case="first-letter" subpages="" canonical="User" xml:space="preserve">Kullanıcı</ns>
      <ns id="3" case="first-letter" subpages="" canonical="User talk" xml:space="preserve">Kullanıcı mesaj</ns>
      <ns id="4" case="first-letter" subpages="" canonical="Project" xml:space="preserve">MusicLexis</ns>
      <ns id="5" case="first-letter" subpages="" canonical="Project talk" xml:space="preserve">MusicLexis tartışma</ns>
      <ns id="6" case="first-letter" canonical="File" xml:space="preserve">Dosya</ns>
      <ns id="7" case="first-letter" subpages="" canonical="File talk" xml:space="preserve">Dosya tartışma</ns>
      <ns id="8" case="first-letter" subpages="" canonical="MediaWiki" xml:space="preserve">MediaWiki</ns>
      <ns id="9" case="first-letter" subpages="" canonical="MediaWiki talk" xml:space="preserve">MediaWiki tartışma</ns>
      <ns id="10" case="first-letter" canonical="Template" xml:space="preserve">Şablon</ns>
      <ns id="11" case="first-letter" subpages="" canonical="Template talk" xml:space="preserve">Şablon tartışma</ns>
      <ns id="12" case="first-letter" subpages="" canonical="Help" xml:space="preserve">Yardım</ns>
      <ns id="13" case="first-letter" subpages="" canonical="Help talk" xml:space="preserve">Yardım tartışma</ns>
      <ns id="14" case="first-letter" canonical="Category" xml:space="preserve">Kategori</ns>
      <ns id="15" case="first-letter" subpages="" canonical="Category talk" xml:space="preserve">Kategori tartışma</ns>
    </namespaces>
  </query>
</api>