Dissertations come in various types, each suited to different academic disciplines. The most common types include empirical dissertations, which involve original research and data collection; non-empirical dissertations, which focus on existing research and theoretical analysis; and case-study dissertations, which provide in-depth analysis of a particular case within its real-life context. Additionally, there's the practice-based dissertation, common in creative fields, combining practical work with an accompanying critical commentary. Each type requires a distinct approach and methodology, tailored to the research question and field of study.