Comma question.. speech usage terms

Question

I have a basic question regarding commas, and I have not found the answer I was looking for.

So the rule of thumb is to never separate the verb from the subject or main subject should I say...but in speech for instance or a question.

E.g

1. Are you ready, Coachella?

We separate -- is that mandatory to use the comma- why? For instance:

2. Are you ready Steven?

vs:

3. Are you ready, Steven?

Another example:

4. It's what she feared the most, death.

Is the comma needed here, and if you reverse it:

5. "Death, it's what she feared most."

Why grammatically does the sentence not work without the comma.

What -term- do you use when you can switch the sentence around and it still works either way ?

Answer 1

In examples 1, 2 and 3:

• the subject is "you";
• "Coachella" and "Steven" are words in the vocative case - they have to be separated from the rest of the sentence by a comma.

Therefore, example 2 is not correct, while 1 and 3 are correct.

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In examples 4 and 5, the situation is different. "Death" is a part of an enumeration with one element. The rule tells that enumerations are separated from the rest of the sentence with a colon, not with a comma:

• It's what she feared the most: death.

• It's what she feared the most: death, spiders and meteors.

and:

• Death: it's what she feared most.

• Death, spiders and meteors: it's what she feared most.

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I am not sure what you mean by this:

What -term- do you use when you can switch the sentence around and it still works either way ?