Bilinear refers to a mathematical function or relationship that involves two variables. In this context, it describes a function that is linear in each of its arguments when the other is held constant. This concept is often used in various fields, including mathematics, computer graphics, and statistics, to analyze and model interactions between two different dimensions or inputs. In practical applications, bilinear interpolation is a common technique used in image processing to estimate pixel values in a grid. By considering the values of four surrounding pixels, it provides a smoother transition between colors or intensities, enhancing the quality of images when resized or transformed.