From Longman Dictionary of Contemporary Englishbrightenbright‧en /ˈbraɪtn/ verb 1 make lighter [transitive] (also brighten something ↔ up)BRIGHT to make something lighter or brighter Use blonde highlights to brighten your hair. The morning sunshine brightened up the room.2 make more attractive [transitive] (also brighten something ↔ up) to make something more colourful or attractive She bought some flowers to brighten the room. I want to brighten the place up a bit.3 make more enjoyable [transitive] (also brighten something ↔ up) to make something more enjoyable, exciting, or interesting His letter brightened my day. I felt I needed something to brighten up my life.4 BRIGHTbecome lighter/brighter [intransitive] to shine more strongly, or become brighter in colour The stage lights brightened to reveal a street scene.5 become sunny [intransitive] (also brighten up) if the weather brightens, the sun begins to shine and it becomes lighter The sky brightened after lunch. Let’s hope the weather brightens up later. It brightened up a bit in the afternoon.6 become happy [intransitive] (also brighten up)HAPPY to become happier or more excited His eyes brightened when we started talking about money. She brightened up a bit when she saw us.→ See Verb table
Examples from the Corpusbrighten• He looked at his watch to find that it was 0228, but still the sky had not begun to brighten.• This brightens and hardens the surface of cutlery so it becomes more resistant to wear and it also removes minor scratches.• At his name, James Whitaker, royal correspondent of the Mirror, brightened as though you had changed his batteries.• The political situation has brightened in recent months.• I read an article in the paper that brightened my day.• Won't that brighten the neighborhood!• Fireworks brightened the sky.• His eyes brightened through his rimless glasses.• Julie brightened up at the thought of visiting home.• But neighbours say it brightens up the area and they want it to stay.• New curtains would brighten up the room.• Flowers are one way to brighten your surroundings.