Tuning fork is a metallic instrument used to assist in tuning of musical instruments and voices.
The tuning fork is shaped like a fork (letter "U") and works with sound vibration. When vibrating, the tuning fork emits the reference note (there) to tune the musical instrument, tuning it.
To use the tuning fork, a certain degree of knowledge of musical notes is necessary (do, re, mi, fa, sol, there, si), since the sound emitted by the tuner must be the same as that of the musical instrument.
However, to help people who do not have keen senses to detect variations in musical notes, there are models of digital tuning forks, which show the differences between the sounds until they are evened out. On the internet, for example, there are online versions of tuning forks, which do not require the use of a metallic instrument, issuing the reference note directly from the computer.
In a figurative sense, the tuning fork is considered a condition model used to compare something.
In its popular usage, the word tuning fork can also mean the "accelerated pace of life," the flurry of personal or professional routine.
The term "tuning fork" is still widely used in legal literature, in the expressions "that tuning fork" or "that same tuning fork", meaning "that same line of thought". It represents a "fine tuning" of the arguments presented by the author of the text.