Q:

What does 50%TTL - 10/90% RF mean for a switching speed measurement?

I understand what switching speed is and why it's important, but I'm confused on the description of switching speed that I commonly see in part specs, like the one below:
Diode Spec with Switching Speed Notes
Many refer to a 50% TTL - 10/90% RF, but what does this actually mean? And what does this tell us about the switching speed?

A:

50% TTL to 90% RF is a measurement of the time from the 50% point of the rising edge of the control signal (for a typical 5V signal this would be 2.5V) and the point at which the rising edge of the RF signal is at 90% (i.e. the point where the signal is 90% "up" the rising edge). 
Likewise, 50% TTL to 10% RF is a similar measurement of the difference in time between the 50% point on the falling edge of the control signal, to the 10% point on the falling edge of the RF signal.

Image and information: https://www.minicircuits.com/app/SW13-2.pdf

