Which term describes the ability of a receiver to detect the presence of a signal?

In radio terminology, 'sensitivity' refers specifically to a receiver's ability to detect very weak signals. A receiver with excellent sensitivity can capture faint, distant stations clearly above the background noise level. It is important to distinguish this from 'selectivity,' which is the receiver's ability to separate a desired signal from other interfering signals on nearby frequencies. While 'RF gain' is a control knob that alters amplification, sensitivity is the actual physical metric of weak-signal detection.