Noun

1. A certain duration of time, a period of time.

   He lectured for quite a long while.

Conjunction

1. During the same time that.

   He was sleeping while I was singing.

   • 1948, Carey McWilliams, North from Mexico / The Spanish-Speaking People of The United States, J. B. Lippincott Company, page 25,

     While De Anza was exploring the Bay of San Francisco, seeking a site for the presidio, the American colonists on the eastern seaboard, three thousand miles away, were celebrating the signing of the Declaration of Independence.

2. although

   This case, while interesting, is a bit frustrating.

3. until

   I'll wait while you've finished painting.