Use 'no-go' when something is not allowed, like a rule or restriction.

Permission Denied

'No-go' also describes plans or ideas that aren't possible to carry out.

Infeasible Plan

'No-go' is casual and usually used in informal speech or writing.

Use 'no-go' as a noun when referring to areas not safe to visit or activities not safe to do.

It can also mean places that are unsuitable for a certain action or use.

Be aware some areas are 'no-go zones' due to cultural or political reasons, not just safety.