Speech-language pathology is a field of expertise practiced by a clinician known as a speech-language pathologist (SLP), also called speech and language therapist, or speech therapist, who specializes in the evaluation and treatment of communication disorders and swallowing disorders.

Speech-language pathologists provide a wide range of services, mainly on an individual basis, but also as support for individuals, families, support groups, and providing information for the general public. Speech-language pathologists (SLPs) work to prevent, assess, diagnose, and treat speech, language, social communication, cognitive-communication, and swallowing disorders in children and adults.

A communicative disorders assistant (CDA) performs hearing and speech-language screenings, prepares therapy materials, implements speech therapy, reports on therapy outcomes, performs routine maintenance on clinical equipment, and works with speech-language pathologists (SLPs) and audiologists to adjust therapy goals. While CDAs cannot perform assessments or set therapy goals, they are a vital part of the therapy team. CDAs are supervised by and work in conjunction with SLPs and audiologists.

While anyone working under the supervision of a speech-language pathologist or audiologist may be considered to be Supportive Personnel, Communicative Disorder Assistants receive their title after being specifically trained and educated in various communicative issues as well as completing field placements in various communication areas (such as fluency, articulation, augmentative and alternative communication, and aural rehabilitation) at various institution types.

Speech services begin with initial screening for communication and swallowing disorders and continue with assessment and diagnosis, consultation for the provision of advice regarding management, intervention and treatment, and provision counseling and other follow up services for these disorders. Services are provided in the following areas:

• cognitive aspects of communication (e.g., attention, memory, problem solving, executive functions).
• speech (phonation, articulation, fluency, resonance, and voice including aeromechanical components of respiration);
• language (phonology, morphology, syntax, semantics, and pragmatic/social aspects of communication) including comprehension and expression in oral, written, graphic, and manual modalities; language processing; preliteracy and language-based literacy skills, phonological awareness.
• swallowing or other upper aerodigestive functions such as infant feeding and aeromechanical events (evaluation of esophageal function is for the purpose of referral to medical professionals);
• voice (hoarseness (dysphonia), poor vocal volume (hypophonia), abnormal (e.g. rough, breathy, strained) vocal quality. Research demonstrates voice therapy to be especially helpful with certain patient populations; individuals with Parkinson's Disease often develop voice issues as a result of their disease.
• sensory awareness related to communication, swallowing, or other upper aerodigestive functions.

Source: wikipedia.org