What is a symbol representing a value that does not change?
I assume you are talking about constant values in expressions. Any letter (including Greek ones) can be used to represent a constatnt, but the most common one is k.
There are, however, some constants which are associated with other symbols:
Ratio of circumference of circle to diameter = pi
Speed of light in vacuum: c
Gravitational attraction: G (not to be confused with g, in the context of the earth's gravity)
Avogardo's constant: NA
To the best of my knowledge there is no symbol for change but the closest would probably be the Dharma wheel which symbolises the cycle of birth death and rebirth. The same thing could be said of growing up but I suppose the closest symbol would be the white lotus which is a symbol representing the attainment of Enlightenment.
Answer £ $ € -- Very valuable! Answer: Assuming the question was about valves there are various symbols for different valve types. (See Link) . Most incorporate intersecting arrowheads (-|><|-) Answer In Algebra, a symbol that represents a value is either a constant (when the value does not change) or a variable (when the value may change).