Philadelphia is just the name of a city. You use it the same way you use any other name in a sentence! Here are a couple of examples.
Philadelphia is a nice place to visit, at least for me it is.
I think Philadelphia cream cheese would be very tasty with these wheat crackers. Let's go to Philadelphia for the weekend. I have a Philadelphia lawyer. I am buying a Philadelphia derringer.
I visited Pennsylvania last summer to explore its historical sites.
i do not know how to use embalming in a sentence. (there is the sentence)
I want to have a gala time with my girlfriend tonight. On July 4th, there is a gala celebration in Philadelphia. The mayor was unable to attend the gala honoring the retired policemen.
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.
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