Revenue Function: A mathematical representation that calculates total revenue based on the number of units sold. Typically denoted as $R(x) = p \cdot x$, where $p$ is the price per unit.
Cost Function: Represents the total cost incurred in producing a certain number of units. Commonly expressed as $C(x) = FC + VC \cdot x$, where $FC$ is fixed costs and $VC$ is variable cost per unit.
Break-Even Point: The level of output at which total revenue equals total costs, resulting in zero profit. It is found by solving $R(x) = C(x)$.