What is the X in X-mas?
A billionth of a second.
Note: The term is often used to refer to a very short time: “He missed having an accident by nanoseconds.”
(ns) 10^-9 seconds; one thousand millionth part of a second.
This is the unit in which the fundamental logical operations of modern digital circuits are typically measured. For example, a microprocessor with a clock frequency of 100 megahertz will have a 10 nanosecond clock period.