That is one of the best books I ever read, but I read it a long time ago and didn't do the exercises.. Nevertheless, I recall the terms cycle and frequency and period very frequently when I was studying CS(computer science), probably from other sources too.
Frequency is number of cycles per second. Measured in Hz (eg some GigaHertz)
Period / Time period, is seconds for a cycle. And is the inverse of frequency. It is represented by the letter T. Measured in s(seconds) (eg some nanoseconds).
Cycle is an FE cycle, a fetch and execute cycle.
See here for example regarding Clock Period (represented by T, and T=1/F) (same thing) http://www.edaboard.com/thread258987.html
This is in physics too if you look up frequency and period and time period the terms are used with waves. An FE cycle can be depicted as a digital wave.
an example here http://cs.nyu.edu/~gottlieb/courses/2000s/2000-01-fall/arch/figs/clock.png
I have a background in computer science but this is the same in physics, and the concept comes from physics and doesn't change anything.
https://simple.wikipedia.org/wiki/Period_(physics)
A Time period (denoted by 'T' ) is the time needed for one complete cycle......Frequency and time Period are in a reciprocal relationship that can be expressed mathematically as: T = 1/f or as: f = 1/T.
In this case Stalling includes an IO element that i'm not used to. I think it's still one single cycle though perhaps not necessarily a processor FE cycle. but one cycle of processor and IO operation. Time period relates to one cycle, always.