/ ˈbraɪtn; NAmE / verb
1.
to become or make sth lighter or brighter in colour :
[ v ]
In the distance, the sky was beginning to brighten.
[ vn ]
a shampoo to brighten and condition your hair
2.
brighten (sth) (up) to become, feel or look happier; to make sb look happier :
[ v ]
Her eyes brightened.
He brightened up at their words of encouragement.
[ vn ]
A smile brightened her face.
3.
brighten (sth) (up) to become or make sth become more pleasant or enjoyable; to bring hope :
[ vn ]
A personal letter will usually brighten up a person's day.
[also v ]
4.
[ vn ] brighten sth (up) to make sth look more brightly coloured and attractive :
Fresh flowers will brighten up any room in the house.
5.
[ v ] brighten (up) ( of the weather ) to improve and become brighter :
According to the forecast, it should brighten up later.
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WORD ORIGIN
Old English (ge)beorhtnian .