A continuous signal or a continuous-time signal is a varying quantity (a signal) whose domain, which is often time, is a continuum (e.g., a connected interval of the reals). That is, the function's domain is an uncountable set. The function itself need not be continuous. To contrast, a discrete time signal has a countable domain, like the natural numbers. A typical example of an infinite duration signal is: A finite duration counterpart of the above signal could be: and otherwise. The value of a finite (or infinite) duration signal may or may not be finite. For example, and otherwise,