The question asks it all really. When referring to a master's degree, do you use an apostrophe or not? That is, is it "a master's" or "a masters"?
I always use "master's degree". Read the following article for more details:
Masters Degree or Master’s Degree? by Maeve Maddox
To answer this question, I’ve consulted the MLA Handbook for Writers of Research Papers, and some university dissertation guidelines.
Speaking generically, you would write master’s degree:
Speaking of a specific degree, you would capitalize Master:
When it comes to abbreviating academic degrees, you’d better check the style book that governs your work.
For example, here is what the guidelines say on the site of Ohio University:
Northeastern University, like the MLA guide, prefers to drop the periods:
Punctuating degrees: Do not include periods in degree abbreviations. [Ex. BS, BA, MA, PhD] The single exception is Hon. for Honorary. –Northeastern University
NOTE: Not all universities use the same abbreviations for the master’s degree:
In my school, University of Nigeria, Nsukka, we use masters". That is the most correct one to use.