Might be better for a math or datacomm exchange, but I'll try here first:
Given that "rate" means the number of times that an event occurs in a unit of time, what is the opposite/inverse of that term? Ie, what is a term for the time between events?
"Latency" comes to mind but is not quite right since it generally refers to the time between cause and effect, not between essentially identical events.
Best Answer
If something is happening repeatedly, we say the value for rate (or frequency) increases if it starts happening more often in a given time-span. Conversely, if it starts happening less often we say the interval is increasing.