The wavy line is
a common sign for water, watercourse, water surface, and the
sea. (The doubling of
it, as in , is a still more common sign for
water.) In nautical charts can represent
In music it is used as an "sound iconic" sign to denote a trill, that is, a quick alternation of two notes a tone or semitone apart.
Placed vertically, , the wavy line in music notation stands for arpeggio, in which tones are played in quick succession, usually toward the higher register: a rising trill.
In some US meteorological systems can mean unstable barometric readings.
As early as about 4,000 years ago the wavy line was also used as a sign for radiation of light and heat. That can be seen in the Babylonian sun sign, , which is similar to the modern , signifying radiation. The fact that the wavy line can mean both water and fiery emanations exemplifies the law of the polarity of meanings of simple graphs.