brightening agent noun

A compound that increases the brightness of a white or coloured textile by converting some of the ultraviolet radiation into visible light

bright-field illumination noun

A method of illumination in microscopy in which the specimen appears dark on a bright background

brightˈwork noun

Polished metal on cars, etc

bright and early

1. Very early
2. In good time

bright-eyed and bushy-tailed (informal)

Eager and alert

bright young thing

A member of the young and fashionable social set in the 1920s and 1930s

look on the bright side

To be hopeful

the bright lights

1. The places of entertainment in a city centre
2. City life, esp as compared with the quiet life of the countryside