"동공" refers to the pupil of the eye, which is the opening in the center of the iris. It allows light to enter the eye, enabling vision. The size of the pupil can change in response to light conditions; it constricts in bright light and dilates in dim light. This adjustment helps regulate the amount of light that reaches the retina. The pupil's size can also be influenced by emotional responses and certain medications. For example, when a person feels excited or scared, their pupils may dilate. Understanding the function of the pupil is essential in fields like optometry and ophthalmology.