The number of subjects can vary greatly depending on the context—whether referring to school subjects, academic disciplines, or fields of study. In general:

• At the school level, students typically study around 6 to 7 subjects per semester, including core subjects like English, math, science, social studies, and physical education, plus electives such as foreign languages and arts.

• A broad classification of academic disciplines includes Humanities, Social Sciences, Natural Sciences, Mathematics, Business, Education, among many others, with each broad field containing multiple specialized subjects.

• For example, common school subjects include English, math, art, science, history, music, geography, physical education, drama, biology, chemistry, physics, information technology, foreign languages, and social studies.

Thus, the exact number of subjects depends on the educational level and the system being considered. For a comprehensive academic classification, there are dozens to hundreds of subjects and sub-disciplines. For typical school curricula, it is usually between 6 and 20 main subjects studied over time.

If a specific type of subjects or educational level is desired, further details can be provided.