# Term for when using a single number is used instead of a function?

A cost per unit could be 20, but it could also be 20 + 2q (in the cast of the latter, the cost per unit is a function whose result increases with each unit produced).

What is the term to describe when a single number is used where we could also expect a function?

I have in mind 'scalar', but I'm not sure if that's the best term.

A cost function can be constant (in $$q$$), but this term is not particular to economics.
• But both $C =20$ and $C=20+q$ are linear and the OP seems to want some terminology for the former not for both (although admittedly I am bit confused by the question). – 1muflon1 Jul 10 '20 at 16:35