when

At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time.

When will they arrive?

Do you know when they arrived?

At what time? At which time? Upon which occasion or circumstance? Used to introduce direct or indirect questions about time.

The site's all bugged. Fix when?

Tank class buff when?

At an earlier time and under different, usually less favorable, circumstances.

He's mister high and mighty now, but I remember him when.

At which, on which, during which: often omitted or replaced with that.

That was the day when the Twin Towers fell.

Not a week goes by when I don't mourn that loss.

The time at, on or during which.

I recall when they were called the Greys.

Next year is when we elect a new mayor.

At (or as soon as) that time that; at the (or any and every) time that; if.

Pavlov's dogs salivate when [i.e. at any and every time that] they hear a bell.

When [i.e. at any and every time that] he speaks to her, he is always polite.

During the time that; at the time of the action of the following clause or participle phrase.

They dream when [i.e. during the time that] they sleep.

I'm happiest when [during the time that, or at any time that] I’m working.

At what time; at which time.

I am here till Friday, when [i.e. at which time] I leave for Senegal.

I was just walking down the street, when [i.e. at which time] all of a sudden it started to rain.

Since; given the fact that; considering that.

I don't see the point of putting up Christmas decorations when I am the only person who is going to see them.

Whereas; although; at the same time as; in spite of the fact that.

You're picking at your scabs when you should be letting them heal.

He keeps changing things when the existing system works perfectly well.

What time; which time.

Since when do I need your permission?

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