One that doesn't vary
Yes - it is Avagadro's number/constant
It is constant for elements. IT depends on number of protons that atom has.
A [real] constant.
Vacuum, if maintained, is a constant as is the number 0 or zero and then there is the number 1
A constant is not a variable at all, and none of its factors was a variable. It is constant.
It means something that doesn't change, like a number.
Such a number is called a "constant". If the number appears in front of a variable, it is sometimes called a "coefficient".
A number with a power is still a number - a fixed constant. The differential of a constant is always 0.
Constant just means that the number does not change. For example, in Chemistry, avogadro's number is 6.022x10^23 and that number will never change, therefore it is a constant.
Constant is a number with no variables. For an example, 12a, but this is a constant 12.
b. the atomic number is constant. The mass number is not constant because there are isotopes of an element that have the same number of protons but different number of neutrons. Likewise, there are isotopes of the same element with different atomic weights.
Such a number is often called a "constant".