An analog input having an input terminal that is measured with respect to a common reference, usually analog ground. It has two input connections, one for the signal being measured and one for the common reference. In multiple input configurations, all signal inputs share the common reference. Input systems that use analog ground as the reference are called Referenced Single-Ended Inputs. Systems that allow an arbitrary reference within the input common-mode range are known as Non-Referenced Single-Ended Inputs. (See also Differential Inputs as a contrasting input type.)

a signal channel that shares a common ground with one or more other signal channels

An analogue input that is measured with respect to a common earth. Single ended inputs are only suitable for signals that are of good size - 100 mV full scale or above.