English definition of “lighten”
LESS SERIOUS [I, T] › If a serious situation lightens, it becomes less serious, and if something or someone lightens it, they make it less serious: Her mood lightened a bit when I asked about her holiday. He tried to lighten the atmosphere by telling a joke.
lighten the burden/load › to reduce the amount of work or trouble someone has to deal with
LESS DARK [I, T] › to become less dark, or to make something less dark: The sun had lightened her hair.