Elizabeth's Fiber & Yarn Store has a nice chart that help compare various yarn weights.
Personally I prefer the WPI (Wraps Per Inch) rather than a name to designate yarn size. If you were told in the pattern that it used yarn at 14 WPI, you could pull out your WPI tool and check to see if the yarn you like gives you 14 WPI regardless what name the manufacture gives it. My WPI tool is a small flash light that I always carry. It used a nail file to mark a line at 0, 1 inch and 2 inches. I pull out my WPI tool and wrap loosly for 2 inches, count the wraps and divide by 2.
If two different yarns give similar WPI they should knit up at a similar gauge.