Focus is a versatile English word with multiple meanings:
1. As a noun: the center of interest or activity ("The focus of our discussion")
2. As a verb: to concentrate attention or effort ("Focus on your work")
3. In photography: the point where light rays converge to form a clear image ("Adjust the focus")
4. In physics: a point at which rays of light, heat, or other radiation meet after being refracted or reflected
5. In geology: the point of origin of an earthquake