What is the role of a loss function in machine learning?

The role of a loss function in machine learning is to evaluate how well predictions align with actual outcomes. This function quantifies the difference between the predicted values generated by the model and the actual values from the training data. By calculating this difference, or "loss," the model can determine how well it is performing. A lower loss indicates a better fit to the training data, guiding the model's learning process.

The loss function serves as a critical feedback mechanism during training, enabling optimization algorithms to adjust model parameters and minimize error. This iterative process helps enhance the model's accuracy and generalization ability on unseen data.

Other options suggest different roles, such as the quality of the training data, optimization methods, or data transformation, which do not directly pertain to the primary function of a loss function in the learning process.