to start looking or feeling happier, or to become lighter and sunnier (about the weather).
She really brightened up when she saw her friends at the party.
A: You look tired. How are you feeling now? B: Much better, thanks! I always brighten up after a good walk.
The weather started to brighten up in the afternoon, which made everyone feel more energetic.
Common mistake
✗She brightened up herself when she heard.
✓She brightened up when she heard.
In this sense 'brighten up' is intransitive — no object. (Cheering someone else is 'brighten up their day'.)
Tell it apart
He brightened up when she walked in.
got happier himself
Flowers brighten up the room.
make the room more cheerful — different sense
You can use 'brighten up' for both people and the weather when they become happier or lighter.Compare with 'cheer up', which is only about mood, not light.
to make something or someone look or feel happier, or to make a place lighter and more cheerful.
A bunch of flowers can really brighten up a room.
A: Sarah seemed upset this morning. B: I brought her some coffee to try and brighten up her day.
Adding some colorful posters can brighten up a classroom and make it a more inviting place to learn.
Common mistake
✗Your message really brightened up me.
✓Your message really brightened me up. / ...brightened up my day.
With a pronoun, the object goes in the middle: 'brighten me up'.
Tell it apart
Some colour would brighten up the office.
make it more cheerful
More lamps would light up the office.
make it physically brighter
Use this sense when you are doing something to improve someone’s mood or the look of a place.Compare with 'decorate', which is only about appearance, not mood.