The cosine similarity measures how close two vectors are to one another using the cosine of the angle between them. Unlike Euclidean distance, the cosine similarity ignores the size of the two vectors, it just focuses on their direction. In {{document retrieval}] and text processing, the cosine similarity is applied to the vector representing the frequencies of words in a document, sometimes weighted by overalll corpus frequency.
Used in Chap. 10: page 141