Which is better to show Label (optional) vs Label (not required)?

1. How do you show something is optional?
2. Does Asterisk mean optional?
3. Is there a symbol for optional?

How do you show something is optional?

The best way to indicate optional is to add the word in parenthesis after the label. It's easy to read and visually connected to the label that it is referring to.

Does Asterisk mean optional?

It is common the use of asterisk (*) to indicate required elements. I understand the use of explicit text is better than relying on symbols. So writing "required" or "optional" is more understandable than relying on some symbol.

Is there a symbol for optional?

Asterisk(*) symbol is used to indicated that item are optional.