I'm scouting some nozzles to fill in gas into a chamber. To get a better understanding of nozzles in general, I'm reading https://en.wikipedia.org/wiki/Nozzle and I stumble already on the second sentence:
A nozzle is often a pipe or tube of varying cross sectional area..
In which way "often"? From my understanding it always provides a varying cross sectional area, otherwise I would simply call it a pipe?