Students: Selecting your project’s category is an important choice with consequences.
Do not assume that your project belongs in the same category that it had in the previous competition.
Every science fair uses its own unique categories and their definitions. Read through all of the category definitions below to find the one that best describes what you studied in your project. For convenience the categories have been organized broadly into groups, but do not limit your category search only to one group. For example, studies of the effects of a chemical on a plant might, depending upon the details, be classified either as Plant Biology (in the Life Science group) or Toxicology (in the Environmental group). Read all of the definitions of possibly relevant categories.
Your category choice will affect what the judges consider.
If your project could possibly belong in more than one category, read this explanation of why your judges may ignore certain aspects of your project.
Your project may be moved to a category different from your preference.
All projects will be reviewed for appropriateness in the requested category by the judges in that category based upon your Project Presentation. Do not assume that your project will remain in the category you request. All such changes in category will be effected by one week prior to the Fair and announced on this web site. If your project’s category is changed, you will be informed directly.

Click on ▶/▼ to expand/hide category definitions.

Life Science Categories

05. Biochemistry/ Molecular Biology
14. Mammalian Biology
17. Microbiology (General)
18. Microbiology (Medical)
20. Plant Biology
24. Zoology

Physical Science Categories

01. Aerodynamics/ Hydrodynamics
02. Alternative Energy
03. Applied Mechanics & Structures
06. Chemistry
12. Electronics & Electromagnetics
15. Materials Science
19. Physics & Astronomy

Mathematical/ Computational Categories

08. Computational Systems & Analysis
09. Computational Systems: Medical
16. Mathematical Sciences

Environmental Categories

10. Earth & Environment: Air/Water
11. Earth & Environment: Soil/Pollution
13. Environmental Engineering
23. Toxicology

Behavioral/ Cognitive Categories

04. Behavioral & Social Sciences
07. Cognitive Science

Product Testing Categories

21. Product Science (Biological)
22. Product Science (Physical)
California Science & Engineering Fair / 2024 / Category Definitions /