Cost Function: A mathematical representation that calculates total cost incurred by producing a certain number of units, usually expressed as $C(x) = F + V \cdot x$, where $F$ is fixed costs and $V$ is variable cost per unit.
Profit Function: A function that calculates profit as the difference between total revenue and total cost, usually expressed as $P(x) = R(x) - C(x)$.
Breakeven Point: $x$ value at which total revenue equals total cost, meaning no profit or loss occurs; found by solving $R(x) = C(x)$.