Monocular cues are visual signals that help us perceive depth and distance using just one eye. These cues include aspects like relative size, where objects that appear smaller are perceived as farther away, and interposition, where one object blocking another suggests that it is closer. Other monocular cues include linear perspective, which involves parallel lines converging in the distance, and texture gradient, where the detail of surfaces decreases with distance. These cues are essential for understanding our three-dimensional environment, even when only one eye is available for viewing.