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.