Speech therapy is the profession specialized in the processes of human communication and swallowing. The speech therapist is the professional specialized in the study, prevention, evaluation, diagnosis and treatment of communication and swallowing difficulties in adults and children. Communication difficulties include voice and speech problems, verbal, oral and written language, non-verbal language and pragmatics, that is, the use of language. [1] [2]
The word speech therapy comes from the Greek logos, which etymologically means logo (word) and paideia (education). Speech therapy deals not only with the spoken and heard word, but also with language. It deals with the articulation of sounds and the voice that makes speech possible, and deals with the reception of sounds and their audibility. Of the language, it studies the processing, the comprehension and the oral and written expression. Non-verbal communication is also a subject of study for speech therapists.
Speech therapy is a field of knowledge that is dedicated to the scientific study of language and communication disorders for their prevention, their diagnostic evaluation and their treatment. The speech therapist professional analyzes the command of the language, its acquisition, the linguistic behaviors outside the norm and the communicative competence of the speaker. He analyzes and acts on the expression and understanding of language.

Speech disorders:

Dislalia
It is an alteration of speech that manifests itself with errors that alter the word in its production. The articulation of the phonemes is altered. The inability for production can occur in a single phoneme (for example “r”) or in a group of phonemes (consonant + “r”). This sound can be perceived correctly, but the person does not produce it by imitation, or in spontaneous speech, or in isolation. Incorrectness persists and can always occur in the same way, it is stable. The reasons for this mispronunciation may be due to altered function of the articulatory organs, which make incorrect or poorly coordinated movements.

Dysglossia
It is the difficulty of oral production caused by anatomical and / or physiological alterations of the peripheral articulatory organs with a central non-neurological origin. There are several causes that can justify a dysglossia: cleft lip, short lingual frenulum, dental anomalies, lingual paralysis, macroglossia, cleft palate or rhinolalia.

Dysphemia
Dysphemia or stuttering is the interruption of the fluency of speech, which affects communication and is accompanied by muscle tension. It is manifested by the repetition of sounds, syllables, blocking at the beginning of the narrative discourse, tension of the face, closing and opening the eyes. The cause is not clear. It is accepted that there is a genetic predisposition and that many factors are involved: biological, psychological, neurological, emotional and social.

Dysarthria
It is a disorder of verbal expression due to an alteration in the muscular control of speech mechanisms. It affects voluntary and involuntary movements. It can occur when there are motor dysfunctions of breathing, phonation, resonance, articulation and prosody.

Voice disorders:

Dysphonia
It is an alteration of the voice in each of its qualities (intensity, tone and timbre). The cause may be a phonation disorder due to changes in the vocal cords due to organic problems (polyps or nodules) or to functional problems of the orophone apparatus, such as the alteration of the vibration of the structures of the larynx. There are dysphonia that last a few days and others that become persistent due to poor use of the voice.

Aphonia
It is the total loss of voice.

Causes:
Diseases of the respiratory system: laryngitis or pharyngitis.
Bad uses of the voice: forcing the voice too much.
Ingestion of toxic or irritating products: smoking, alcohol, etc.
Nervous causes: a hoarse voice, or with a different timbre or intensity can appear in certain cases of nervousness.
Manipulations of the larynx: certain operations or medical procedures such as an operation for polyps, can cause aphonia or voice changes.
Excessive cold: the contact of cold with the throat.

Language disorders:

Speech delay
It is an alteration in the development of the acquisition of speech that makes it quite unintelligible. There is a mismatch between the evolution of phonetic and phonological competences and the set of other linguistic abilities. It assumes little ability in the domain of speech, although there may be good understanding of the language. Phonetics and phonology are two complementary linguistic disciplines, which are related to speech delay.

Language delay
It is a delay in the appearance or in the development of all levels of language (phonological, morphosyntactic, semantic and pragmatic), which mainly affects expression and, to a lesser extent, comprehension.

Specific language disorder (SLI)
It is a language disorder of diverse and often unknown etiology, which manifests itself in various linguistic dysfunctions. Specific language disorder refers to a set of innate, persistent and specific difficulties for the acquisition and management of the linguistic code. Language arises with delay and does so with marked distortions that differentiate it from simple language delay, and they are persistent because, either permanently accompanies the child throughout his life, or in less serious cases, after speech therapy , the affectation of the language can manifest with difficulties in the construction of the complex speech or interfering in the acquisition of the reading and writing process.

Aphasia
It is a brain disorder characterized by the more or less exclusive loss of the production and / or comprehension of spoken or written language, or both, without injuries to the phonation apparatus or mental illnesses. Its origin is diverse. Due to vascular or traumatic injury, due to the existence of a tumor, a cerebrovascular accident, a brain infection or a neoplasm. The expression is not fluent, there is a lot of difficulty in articulating the words, the sentences have an altered syntax and there are problems in finding the words that assign the name to things. The understanding is quite preserved. Apparently it may seem that they have not heard well what they are saying and what happens is that there is a serious problem of understanding. These patients speak a lot and fluently, although the speech may seem inconsistent because they do not take into account the interlocutor.