It is normally assumed that a constant term, such as "Napoleon" has a definite meaning, but it is noteworthy that in both logic and mathematics constants tend to be written as letters from the beginning of the alphabet, like "a", "b", "c" (as distinct from variables from the end of the alphabet). In mathematics, a good example is y = ax + b as the equation defining "an arbitrary linear function, with constants a and b".

Again, such and other schematic constants are often called "parameters" if they are supposed to be of a certain understood (implicitly or specified) kind or range - as when it is added to the above example "with a and b rational or real, and a not 0".

Next, there are specific constants, such as logical constants, = or identity, and also interpunction constants, like dots, commas, brackets, and linefeeds.