Most colleges and universities abbreviate the names of their degrees based on the full name of the English translation of the original Latin name for the degree. For example, the Latin term "artium baccalaureus" is literally translated into English as "Bachelor of Arts." Abbreviating the key terms in the translation would make the proper abbreviation of this specific degree "B.A."
The names of medical and doctoral degrees are abbreviated in a very specific way to indicate the area of study in which an individual has excelled. Generally, these are abbreviated in the Latin spelling manner. For example, the Doctor of Philosophy degree is abbreviated as "Ph.D." (philosophiae doctor). The Doctor of Medicine degree is abbreviated as "M.D." (medicinae doctor).
Certain universities use a traditional Latin method to abbreviate the names of specific undergraduate degrees, while others do not. Harvard University is an example of a school that uses the Latin method of abbreviation. This requires abbreviating the Bachelor of Arts degree as "A.B." (artium baccalaureus) and the Bachelor of Science degree as "S.B." (scientiae baccalaureus).
It is a policy of certain universities to use periods in between the letters of a degree abbreviation, while others do not. The University of Colorado is an example of a university that does not use periods in its degree abbreviations. For example, a Master of Arts degree would traditionally be abbreviated as "M.A.," but at universities that do not use periods, it would be written after a person's name as simply "MA."