(interrogative) Used to introduce questions about time.
‘When will they arrive?’;
Supposing that, assuming that, in the circumstances that; used to introduce a condition or choice.
‘If it rains, I shall get wet.’;
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?’;
(computing) In the event that a statement is true (a programming statement that acts in a similar manner).
‘If A, then B, else C.’;
At an earlier and less prosperous time.
‘He's mister high and mighty now, but I remember him when.’;
Supposing that; used with past or past perfect subjunctive indicating that the condition is closed.
‘I would prefer it if you took your shoes off.’; ‘I would be unhappy if you had not talked with me yesterday.’; ‘If I were you, I wouldn't go there alone.’;
(indirect question) Used to refer to doubts about time.
Supposing that; given that; supposing it is the case that.
‘If that's true, we had better get moving!’;
(relative) At which, on which, during which. Often omitted or replaced with that.
‘That was the day when the Twin Towers fell.’;
Although; used to introduce a concession.
‘He was a great friend, if a little stingy at the bar.’;
At what time.
‘They were told when to sleep.’; ‘He doesn't know when to stop talking.’;
Whether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs.
‘I don't know if I want to go or not.’;
At such time as.
‘I’m happiest when I’m working.’;
(usually hyperbolic) Even if; even in the circumstances that.
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.’;
Introducing a relevance conditional.
‘I have leftover cake if you want some.’;
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.’;
(informal) An uncertainty, possibility, condition, doubt etc.
(interrogative) What time; which time.
‘Since when do I need your permission?’;
In case that; granting, allowing, or supposing that; - introducing a condition or supposition.
‘Tisiphone, that oft hast heard my prayer,Assist, if dipus deserve thy care.’; ‘If thou be the Son of God, command that these stones be made bread.’;
The time at which something happens.
‘A good article will cover the who, the what, the when, the where, the why and the how.’;
Whether; - in dependent questions.
‘Uncertain if by augury or chance.’; ‘She doubts if two and two make four.’;
That's enough, a command to stop adding something, especially an ingredient of food or drink.
At what time; - used interrogatively.
‘When shall these things be?’;
At what time; at, during, or after the time that; at or just after, the moment that; - used relatively.
‘Kings mayTake their advantage when and how they list.’; ‘Book lore ne'er served, when trial came,Nor gifts, when faith was dead.’;
While; whereas; although; - used in the manner of a conjunction to introduce a dependent adverbial sentence or clause, having a causal, conditional, or adversative relation to the principal proposition; as, he chose to turn highwayman when he might have continued an honest man; he removed the tree when it was the best in the grounds.
Which time; then; - used elliptically as a noun.
‘I was adopted heir by his consent;Since when, his oath is broke.’; ‘Come hither; mend my ruff:Here, when! thou art such a tedious lady!’; ‘When as sacred light began to dawn.’; ‘When that mine eye is famished for a look.’;
as soon as;
‘once we are home, we can rest’;