When referring to the possessive form of a master’s degree, “master’s” is the correct term. As an example:
So, if you’re talking about a master’s degree, you’d say “master’s” to indicate possession or association.
But to break this down to its proper format, this is what you need to know—when a person receives a master’s degree, it is acknowledged that they have sufficient knowledge in a subject of study to be regarded as a master of it. As a result, a master’s degree should be spelled with an apostrophe to highlight that it is a master’s degree (possessive – for someone who has it).
If one refers to a specialized field, such as a Master of Arts, one should drop the apostrophe and the ‘s.’ However, this rule is somewhat blurred in the age of email and text messaging, and increasingly, “master,” “masters,” and “master’s” have become correct and acceptable ways to spell and refer to a master’s degree.