The Code of Student Conduct defines cheating for the UC Berkeley campus:
Cheating is defined as fraud, deceit, or dishonesty in an academic assignment, or using or attempting to use materials, or assisting others in using materials, that are prohibited or inappropriate in the context of the academic assignment in question. 
Here are some examples: 
- Copying or attempting to copy from others during an exam or on an assignment.
- Communicating answers with another person during an exam.
- Pre-programming a calculator or other personal electronic device to contain answers, or using other unauthorized information for exams.
- Using unauthorized materials, prepared answers, written notes, or concealed information during an exam.
- Allowing others to do an assignment or a portion of an assignment for you, including the use of a commercial term-paper service.
- Submitting the same assignment for more than one course without prior approval of all the instructors involved.
- Collaborating on an exam or assignment with any other person without prior approval from an instructor.
- Taking an exam for another person or having someone take an exam for you.
- Altering a previously graded exam or assignment for the purpose of a grade appeal or of gaining points in a re-grading process.
- Submitting an electronic file the student knows to be unreadable or corrupted instead of a completed assignment. The student then has extra time to finish the assignment without penalty.
If you determine that a student very likely did cheat, you need to follow through to some kind of resolution. This is dealt with on the Teaching Guide page If You Encounter Academic Misconduct.
 Berkeley Campus Code of Student Conduct, Appendix 2 (p. 25).  Examples are from the Center for Student Conduct, Student Code of Conduct Violations.