# 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.

• In this case (cost functions), what do you think of the term 'unit cost' Jul 10 '20 at 15:48
• I think that unit cost (or rather cost per unit) is something like average cost. Average cost may be constant and may also change, so again I would just say constant average (or constant marginal) cost. Jul 10 '20 at 16:01

I guess the term you're looking for is Linear Cost function?

• 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
• But he said cost per unit. So the first one is linear, the second one is a quadratic cost. But yeah, its kinda confusing.
– user28372
Jul 10 '20 at 16:39
• oh I did not catch that, my bad.
– 1muflon1
Jul 10 '20 at 16:41