There is no widely accepted definition of the term sensitive topics, even though most survey researchers would probably agree that certain subjects, such as income, sex, and religion, are definitely examples of the concept. In their classic text Asking Questions: A Practical Guide to Questionnaire Design, Seymour Sudman and Norman Bradburn avoided the term altogether and instead talked about "threatening" questions.

Part of the problem is that topics or questions can be sensitive in at least three different, though related, senses. The first sense is that of intrusiveness. Some questions are inherently offensive to some (or most) respondents; some topics are seen as inappropriate for a survey. Respondents may find it offensive to be asked about their religion in a government survey or about their income ...