Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In complex analysis, a mathematical discipline, a Stokes line is named after Sir George Gabriel Stokes, is a line in the complex plane which ''turns on'' different kinds of behaviour when one ''passes over'' this line although, somewhat confusingly, this definition is sometimes used for anti-Stokes lines. This article follows the former definition, more common in mathematical literature (but less common in physics literature). When approximating integral equations it is vital to know where the Stokes lines are so as to keep track of exponential smallness.