What does "RST" stand for in a signal report?

In amateur radio, the RST system stands for Readability, Strength, and Tone. 'Readability' is scaled from 1 to 5 and describes how easy it is to understand the signal. 'Strength' is scaled from 1 to 9 and measures how powerful the received signal is. 'Tone' is also scaled from 1 to 9, but is primarily used for Morse code (CW) or digital transmissions to describe the musical purity of the received tone. Distractors like 'tempo', 'speed', or 'recovery' are not standard terms used in amateur radio signal reporting.