title: Is this a one to many or many to many relationship?
body: <p>So I'm making an E/R diagram based on drugs. It states that each drug is produced by a given pharmaceutical company and the trade name of the drug is identified among the products of the given pharmaceutical company. So here's the E/R diagram I drew up:
  <a href="https://i.stack.imgur.com/EC2Od.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EC2Od.png" alt="E/R diagram"></a>
  Now the biggest question I have about this is, are these relationships supposed to be one to many or many to many? Each one relationship is represented by an arrow (where the pointed arrow means at most one and the rounded arrow means exactly one). I first assumed that a single drug identified by a single trade name would come from just one pharmaceutical company but would it be possible for a single drug to come from multiple pharmaceutical company's? I'm also not sure if it's supposed to be a 3 way relationship or not. </p>