What is the name of the symbol used to denote a ratio?

Answer 1

A colon is used between the number of a ratio.

(A colon is also used to separate the digits of a sexagesimal (base 60) number used to represent seconds (or minutes) since midnight, ie the time of day.)

Answer 2

I do not think it has a formal name other than "the ratio symbol " written as : : ". Sort of like the "=" sign is called "the equal sign"

Answer 3

It is a colon.