bachelor : a person who has received what is usually the lowest degree conferred by a four-year college, university, or professional school.
Another masters degree for which most undergraduates did not major in that field is the MBA (Masters of Business Administration). This is a two year program. In addition there are many similar masters like Masters of Public Administration or Masters of Public Policy given at Schools of Public Administration and the like. Many universities offer one or two year programs resulting in a masters of internatinal relations or masters of development economics to students interested in international work. All of these masters degrees generally require only course work and no thesis.
The MS and MA degrees much more commonly do require a thesis. These theses are nowhere near as difficult to do as a PhD dissertation.
Some universities (M.I.T. for one) offer a Sc.D. as well as a Ph.D. The former is a Doctor of Science (though in Latin which is why the word order seems wrong). 30 years ago you could have your choice of an ScD or PhD if your area was one of the “hard” sciences but not, for example, in Economics which only offered a PhD.