When and Until

Question: What is the difference between when and until?

Grammar: Adverbs (time expressions)

In a way, these two words are opposites. Have a look at the following timelines:

6:00 pm – I start writing.

7:00 pm – Dinner is ready.

7:00 pm – I stop writing and eat dinner.

For this situation, you can say both:

I stopped writing when dinner was ready.

I wrote until dinner was ready. Until often is used to show a surprising situation. Consider:

John could speak when he was 8.

John couldn’t speak until he was 8.

In the first sentence, we are not sure when he started speaking; only that he could at 8 years old. In the second sentence, we are clearly surprised because 8 is very late to start speaking.