Fans are encouraged to donate to help cover costs but it is entirely optional.

Additional information - this is entirely optional but, if provided, should follow one of the three possible keywords:

Pre-school education is entirely optional, and exists to aid in the development of children under 6.

That's entirely optional, we'll talk again about that next week.

In some of the arts and language subjects lectures were seen as entirely optional in my day.

Our trips and good times programmes are of course entirely optional.

Supporters of the game argue that many of these rules and charts are entirely optional.

In most cases, the information provided on a form is entirely optional.

David Gaider says the romance of all flavors is entirely optional.

This comes in the form of an ice cube down your front or back, but is entirely optional.