Word for "a thing that is derived from."

I have some code containing "derivations" which are values that update automatically when any of the values it uses are updated. They are derived from these sub-values, but I don't know what to call them.

I could have sworn there was a math term for it, but I can't seem to find it.

As an example of the term, I've tried searching "derivee" and "derivation source," and checked the thesaurus for "derive."

Is there a single word for the values from which another value is derived?

Also, these aren't arguments for a function, but more like a column in a spreadsheet which some other column is dependent on.


I'm pretty sure I've heard the simple term 'precursor' used in a mathematical sense.

precursor n.

  1. [A person, situation etc – licensed by the example] that precedes and indicates, suggests, or announces someone or something to come

[AHD]

The 'source giving rise to a related entity' implication is certainly present in the chemical usage:

precursor 3. (Chemistry)

a chemical substance that gives rise to another ... substance

[Collins]

and in the biology usage:

precursor 4

a cell or tissue that gives rise to a variant ... form.

[RHK Webster's]


How about independent variable?

Independent variables are the variables that the experimenter changes to test their dependent variable. A change in the independent variable directly causes a change in the dependent variable

https://www.thoughtco.com/definition-of-independent-variable-605238