There are two different uses of the word “when”.
1. In questions, in which we want to know the time something happens: (bold words stressed)
When do you leave for work?
When do you have your breakfast?
"When" in above sentences, together with what, where, why and how are called interrogatives. When used in this way, these are content words and are usually stressed, i.e. accented.
2. When “when” is not a question word: used as a function word, spoken with normal tone and not accented.
a. "When" part tells what happens first:
When we saw Bob, we told him the news
We told Bob the news when we saw him.
b. "When" part indicates a condition, situation, etc. (The syllables may be accented are shown in bold)
He is impatient when he is kept waiting.
We have only three books when we need five.
How can I help you when I can’t help myself?
Stand up when your name is called.
