In mathematics, equations that define functions are often written using function notation. Functions are typically assigned single-letter names, most commonly $f$, $g$, $h$, $F$, $G$, or $H$. For a function named $f$, the notation specifies the relationship between an input value $x$ and its corresponding output value $y$ as $y = f(x)$. In this notation, $x$ represents the domain value, and $f(x)$ represents the corresponding range value. The expression $f(x)$ is read as '$f$ of $x$' or 'the value of $f$ at $x$'. The parentheses in this context indicate the input parameter mapping to the function and do not indicate multiplication.