M.A. is an abbreviation for master of arts. M.S. is an abbreviation for master of sciences. Both graduate degrees have been used for students of Communication Disorders depending on the university attended and the year.
C.C.C. is an abbreviation for Certificate of Clinical Competence. Speech pathologists that have passed a national exam and did a clinical fellowship year with proper accreditation from the American Speech Language and Hearing Association will have those letters after their name.
S.L.P is an abbreviation for Speech-Language Pathologist, a certification awarded by the Americah Speech-Language-Hearing Association (ASHA)