title: What is "Hadoop" - the definition of Hadoop?
body: <p>It is kind of obvious and we will all agree that we can call <code>HDFS + YARN + MapReduce</code> as <em>Hadoop</em>. But what happens with different other combinations and other products in the <em>Hadoop</em> ecosystem?</p>
  
  <p>Is, for example, <code>HDFS + YARN + Spark</code> still <em>Hadoop</em>? Is <code>HBASE</code> <em>Hadoop?</em> I guess we consider <code>HDFS + YARN + Pig</code> <em>Hadoop</em>, since <em>Pig</em> uses <em>MapReduce.</em></p>
  
  <p>Are only the <em>MapReduce</em> tools considered <em>Hadoop</em>, but anything else run on <code>HDFS + YARN</code>(like <em>Spark</em>) is <em>non Hadoop</em>?</p>