When academic degrees are mentioned in a generic way, often in combination with a field of study, lowercase both the degree and field and use the possessive form (except for the doctorate degree).
associate’s degree in communications
bachelor’s degree in chemistry
doctorate [or doctoral] degree in linguistics
master’s degree in creative writing
When academic degrees take the form of a spelled-out version of the official name of the degree (e.g., BA, MFA, BS, PhD, etc.), capitalize and don’t use the possessive form. However, lowercase the field unless it is a proper noun.
Bachelor of Science in mathematics
Doctor of Philosophy in ethnomusicology
Master of Arts in English
Master of Fine Arts in painting
The abbreviations of degrees take no periods. (See related rules about abbreviation.) Here is a short list of common degrees at Cornell:
BA (Bachelor of Arts)
BS (Bachelor of Science)
JD (Juris Doctor)
MA (Master of Arts)
MArch (Master of Architecture)
MBA (Master of Business Administration)
MD (Doctor of Medicine)
MEng (Master of Engineering)
MPA (Master of Public Administration)
MPS (Master of Professional Studies)
MS (Master of Science)
PhD (Doctor of Philosophy)