Unprecedented means something that has never happened before. Some people may use the word as something they've never seen before, but it really means something that has never been preceded by the same thing.
The home run record set by Barry Bonds is unprecedented.
i do not know how to use embalming in a sentence. (there is the sentence)
So- you are asking when to use 'when' in a sentence. When you are asking how to use when in a question, you are already using when in a sentence, because a question actually is a sentence. I like to use when in a sentence whenever I like.
How do you use sedition in a sentence
use contingency in a sentence?
use adainty as sentence
Can you use abstemious in a sentence?
use inmates in sentence
use figureatively in a sentence
Use it in a big sentence.
can i use polymer in a sentence
.. how can use scrum in a sentence
"I can use 'salutary' in a sentence!"