# How is a procedure application a control structure?

In scheme, a procedure application is considered as a control structure. Why is this?

• What is your source for this? Where have you looked for an explanation? [That tag had nothing to do at all with your question...[ – Raphael Apr 9 '16 at 14:31

The answer will depend on how you define "control structure", for which there are probably $n+1$ versions out there.