title: what is a 'layer' in a neural network
body: <p>Below I've drawn a typical feed forward neural network:</p>
  
  <p><a href="https://i.stack.imgur.com/KBY0x.png" rel="noreferrer"><img src="https://i.stack.imgur.com/KBY0x.png" alt="Typical Feed Forward Neural Network"></a></p>
  
  <p>Now my question is, as far as lingo goes, what is a layer?</p>
  
  <p>Could each individual process (rectangle) be considered a layer? or is a layer the combination a single row of the flow diagram? I sometimes see the Multiply + Add as a single layer, and the nonlinear function (relu) as a separate layer. But I would really appreciate a definitive answer.</p>
  
  <p>I often find on online videos teaching people about Neural Networks, the instructors themselves mix up the number of layers within a single example. </p>