Sun-up is a term often used to describe the moment when the sun first appears over the horizon at the beginning of a new day. However, there are many other words that can be used to describe this event. One of these words is dawn, which refers to the early morning hours when the sky starts to brighten with the first light of day. Another word that can be used in place of sun-up is sunrise, which refers specifically to the moment when the sun becomes fully visible above the horizon. Other options include daybreak, first light, and morning light, all of which describe the transition from darkness to light at the start of a new day.