For text classification.
From Introduction to Information Retrieval by Christopher D. Manning, Prabhakar Raghavan & Hinrich Schütze, Text classification and Naive Bayes:
"general classes are usually referred to as topics, and the classification task is then called text classification, text categorization, topic classification, or topic spotting"
http://mallet.cs.umass.edu/topics.php http://www.cs.princeton.edu/~blei/topicmodeling.html