“While” is a word in the English language that functions both as a noun and as a subordinating conjunction. Its meaning varies largely based on its intended function, position in the phrase and even the writer or speaker’s regional dialect. As a conjunction, it is synonymous with the word “whilst”, a form often considered archaic in American English, as well as in some style guides on both sides of the Atlantic.
An uncertain duration of time, a period of time.
“He lectured for quite a long while.”
During the same time that.
“He was sleeping while I was singing.”
“This case, while interesting, is a bit frustrating.”
“I’ll wait while you’ve finished painting.”
As long as.
“While you’re at school you may live at home.”
To pass (time) idly.
Used to introduce questions about time.
“When will they arrive?”
Used to introduce indirect questions about time.
“Do you know when they arrived?”
“Do you know when they will arrive?”
“Do you know when they arrive?”
At an earlier and less prosperous time.
“He’s mister high and mighty now, but I remember him when.”
Used to refer to doubts about time.
At which, on which, during which. Often omitted or replaced with that.
“That was the day when the Twin Towers fell.”
At what time.
“They were told when to sleep.”
“He doesn’t know when to stop talking.”
At such time as.
“I’m happiest when I’m working.”
At the time of the action of the following clause or participle phrase.
“It was raining when I came yesterday.”
“The show will begin when I get there.”
“The game is over when the referee says it is.”
“Be careful when crossing the street.”
“Pay attention when spoken to.”
“When (you are) angry, count to ten before speaking or acting.”
“That time when the dog stole the turkey from the table.”
Since; given the fact that.
“I don’t see the point of putting up Christmas decorations when I am the only person who is going to see them.”
What time; which time.
“Since when do I need your permission?”
The time at which something happens.
“A good article will cover the who, the what, the when, the where, the why and the how.”
That’s enough, a command to stop adding something, especially an ingredient of food or drink.