GREP (global/regular expression/print) is a way to describe patterns in text. For example, if you want to find a word that starts with a 'D' and ends with a 'G', you can do that with GREP.
Particularly useful for long documents such as books, catalogues or newspapers, the power of GREP can be harnessed to deal with the removal of double spaces after full stops or to apply a style to every string of text inside a set of parenthesis.
GREP works by using a series of codes, known as expressions, to match strings of text, characters or numbers. By combining these codes into expressions, we can create very loose or very precise matches, far beyond the usual 'Find and Replace' functionality. Even better, with InDesign CS4's support for GREP styles we can set up rules that will automatically style match text, even if it's added after you've formatted the document. In this tutorial we're going to set up some automatic formatting for a food and recipe magazine.