The function "ln(x)" represents the natural logarithm of x, which is the logarithm to the base e. The number e is an important mathematical constant approximately equal to 2.71828. The natural logarithm is used to solve equations involving exponential growth or decay, making it essential in fields like mathematics, physics, and finance. The domain of ln(x) is x > 0, meaning it is only defined for positive numbers. As x approaches zero, ln(x) approaches negative infinity, while as x increases, ln(x) also increases, but at a decreasing rate. This behavior makes ln(x) useful for modeling various natural phenomena.