Here are some examples:
* "The circus put on a great show." (The show is the event itself)
* "She's a star of the Broadway show." (The show is a specific performance)
* "The fashion show was a hit." (The show is a presentation of clothing)
However, "show" can also be a verb:
* "Show me your new toy."
* "They will show the movie next week."
So, it depends on the context. If you're unsure, look at how the word is used in the sentence.