Clinical linguistics is the branch of linguistics that applies linguistic concepts and theories to the study of language disorders. As the name suggests, clinical linguistics is a dual-facing discipline. Although the conceptual roots of this field are in linguistics, its domain of application is the vast array of clinical disorders that may compromise the use and understanding of language. Both dimensions of clinical linguistics can be addressed through an examination of specific linguistic deficits in individuals with neurodevelopmental disorders, craniofacial anomalies, adult-onset neurological impairments, psychiatric disorders, and neurodegenerative disorders. Clinical linguists are interested in the full range of linguistic deficits in these conditions, including phonetic deficits of children with cleft lip and palate, morphosyntactic errors in children with specific language impairment, and pragmatic language impairments in adults with schizophrenia. Like many applied disciplines in linguistics, clinical linguistics sits at the intersection of a number of areas. The relationship of clinical linguistics to the study of communication disorders and to speech-language pathology (speech and language therapy in the United Kingdom) are two particularly important points of intersection. Speech-language pathology is the area of clinical practice that assesses and treats children and adults with communication disorders. All language disorders restrict an individual’s ability to communicate freely with others in a range of contexts and settings. So language disorders are first and foremost communication disorders. To understand language disorders, it is useful to think of them in terms of points of breakdown on a communication cycle that tracks the progress of a linguistic utterance from its conception in the mind of a speaker to its comprehension by a hearer. This cycle permits the introduction of a number of important distinctions in language pathology, such as the distinction between a receptive and an expressive language disorder, and between a developmental and an acquired language disorder. The cycle is also a useful model with which to conceptualize a range of communication disorders other than language disorders. These other disorders, which include hearing, voice, and fluency disorders, are also relevant to clinical linguistics. Clinical linguistics draws on the conceptual resources of the full range of linguistic disciplines to describe and explain language disorders. These disciplines include phonetics, phonology, morphology, syntax, semantics, pragmatics, and discourse. Each of these linguistic disciplines contributes concepts and theories that can shed light on the nature of language disorder. A wide range of tools and approaches are used by clinical linguists and speech-language pathologists to assess, diagnose, and treat language disorders. They include the use of standardized and norm-referenced tests, communication checklists and profiles (some administered by clinicians, others by parents, teachers, and caregivers), and qualitative methods such as conversation analysis and discourse analysis. Finally, clinical linguists can contribute to debates about the nosology of language disorders. In order to do so, however, they must have an understanding of the place of language disorders in internationally recognized classification systems such as the 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5) of the American Psychiatric Association.
In the linguistic literature, the term theme has several interpretations, one of which relates to discourse analysis and two others to sentence structure. In a more general (or global) sense, one may speak about the theme or topic (or topics) of a text (or discourse), that is, to analyze relations going beyond the sentence boundary and try to identify some characteristic subject(s) for the text (discourse) as a whole. This analysis is mostly a matter of the domain of information retrieval and only partially takes into account linguistically based considerations. The main linguistically based usage of the term theme concerns relations within the sentence. Theme is understood to be one of the (syntactico-) semantic relations and is used as the label of one of the arguments of the verb; the whole network of these relations is called thematic relations or roles (or, in the terminology of Chomskyan generative theory, theta roles and theta grids). Alternatively, from the point of view of the communicative function of the language reflected in the information structure of the sentence, the theme (or topic) of a sentence is distinguished from the rest of it (rheme, or focus, as the case may be) and attention is paid to the semantic consequences of the dichotomy (especially in relation to presuppositions and negation) and its realization (morphological, syntactic, prosodic) in the surface shape of the sentence. In some approaches to morphosyntactic analysis the term theme is also used referring to the part of the word to which inflections are added, especially composed of the root and an added vowel.