Paraphrasing of copyrighted material may, under certain circumstances, constitute copyright infringement. In most countries that have national copyright laws, copyright applies to the original expression in a work rather than to the meanings or ideas being expressed. Whether a paraphrase is an infringement of expression, or a permissible restatement of an idea, is not a binary question but a matter of degree. Copyright law in common law countries tries to avoid theoretical discussion of the nature of ideas and expression such as this, taking a more pragmatic view of what is called the idea/expression dichotomy. The acceptable degree of difference between a prior work and a paraphrase depends on a variety of factors and ultimately depends on the judgement of the court in each individual cas