阳光 (yáng guāng) is the concrete noun for sunlight — the light and warmth from the sun. It is more specific than 光明 (guāng míng), which means brightness or light in a general sense (e.g., a bright room or a promising future). At HSK4, 阳光 is used literally; its colloquial meaning of 'upbeat' is less common at this level.