Definitions are useless, what one needs is a notion: a smallest working model of censorship. If a store doesn't have a particular book, it can be to a multitude

Definitions are useless, what one needs is a notion: a smallest working model of censorship. If a store doesn't have a particular book, it can be to a multitude of reasons. But what if one removes an existing book from a library? The book is not physically different from others, nor does it carry some unusual associated costs, it could be standing happily there for many more years. So why it's singled out? Because of what it contains? This is where we call it censorship. (Note that what exactly it contains is irrelevant.) In this case the book as a product is not different from a trillion of other Amazon products. What makes it different is its content. So yes, this is censorship.