When is Scrum applicable?

Over the years, I was oftened asked the question: "Is Scrum applicable in this context?" or alternatively "When or under which circumstances can I apply Scrum?". I gave (and read) lots of more or less sophisticated answers to that question, but have a very simple approach to answer this now.

You are able to (and probably should) do Scrum if:

1. You are able to fill a Product Backlog
2. You have - or can establish - a Team (which means team - not group!)
3. You have - or can establish - a Product Owner
4. You have - or can establish - a Scrum Master

That's it.

Of course you can still use several single practices and tools of the Scrum framework if these conditions are not fullfillable - which is not a sin. But you should not call it "Scrum" then!