... is ALWAY WRONG. The correct term is "f/stop" or in some cases "f/stop number". The punctuation is critical to proper understanding. It is a fraction and must be written with a slash. Also the standard in optical formulas is to us a lower case "f" for focal length so it is always "f/stop" or "f/8" and never "F/stop" or "F/8" with the possible exception of full English sentences where the term begins the sentence.
I never refer to "f/stop number" except when explaining f/stops. I always just use "f/stop". I generally use "stop down" and "open up" when referring to changing the f/stop.
With shutter speeds I refer to them as the fractions they are. The only time I refer to a shutter speed using the denominator only would be when describing the adjustment to a novice saying something like "to set it to 1/125 you turn the dial until the display says '125'".
