Webster's Revised Unabridged Dictionary · 1913

Brighten

Brighten ({not transcribed}) , transitive verb

[From Bright, a.]

1.
To make bright or brighter; to make to shine; to increase the luster of; to give a brighter hue to.
2.
To make illustrious, or more distinguished; to add luster or splendor to.
The present queen would brighten her character, if she would exert her authority to instill virtues into her people. — Swift
3.
To improve or relieve by dispelling gloom or removing that which obscures and darkens; to shed light upon; to make cheerful; as, to brighten one's prospects.
An ecstasy, which mothers only feel, Plays round my heart and brightens all my sorrow. — Philips
4.
To make acute or witty; to enliven. — Johnson

Brighten , intransitive verb

[Anglo-Saxon beorhtan.]

To grow bright, or more bright; to become less dark or gloomy; to clear up; to become bright or cheerful.
And night shall brighten into day. — N. Cotton
And, all his prospects brightening to the last, His heaven commences ere world be past. — Goldsmith