<unk>  is best thought of as a collection of different disorders, rather than a single problem. Each individual with<unk>  will present with their own particular combination of language strengths and weaknesses. Consequently, it is a major challenge just to document the various difficulties that can occur in different people, let alone decide how they might best be treated. Most classifications of the<unk> s tend to divide the various symptoms into broad classes. A common approach is to distinguish between the fluent<unk> s (where speech remains fluent, but content may be lacking, and the person may have difficulties understanding others), and the nonfluent<unk> s (where speech is very halting and effortful, and may consist of just one or two words at a time). However, no such broad-based grouping has proven fully adequate. There is wide variation among people even within the same broad grouping, and<unk> s can be highly selective. For instance, people with naming deficits (anomic<unk>  might show an inability only for naming buildings, or people, or colors. It is important to note that there are typical difficulties with speech and language that come with normal aging as well. As we age, language can become more difficult to process resulting in a slowing of verbal comprehension, reading abilities and more likely word finding difficulties. With each of these though, unlike some<unk> s, functionality within daily life remains intact. Boston classification + Major characteristics of different types of<unk>  according to the Boston classification Type of<unk>  Speech repetition Naming Auditory comprehension Fluency Expressive<unk>  (Broca's<unk>  Moderate–severe Moderate–severe Mild difficulty Non-fluent, effortful, slow Receptive<unk>  (Wernicke's<unk>  Mild–severe Mild–severe Defective Fluent paraphasic Conduction<unk>  Poor Poor Relatively good Fluent Mixed transcortical<unk>  Moderate Poor Poor Non-fluent Transcortical motor<unk>  Good Mild–severe Mild Non-fluent Transcortical sensory<unk>  Good Moderate–severe Poor Fluent Global<unk>  Poor Poor Poor Non-fluent Anomic<unk>  Mild Moderate–severe Mild Fluent * Individuals with receptive<unk>  (Wernicke's<unk> , also referred to as fluent<unk> , may speak in long sentences that have no meaning, add unnecessary words, and even create new "words" (neologisms). For example, someone with receptive<unk>  may say, "delicious taco", meaning "The dog needs to go out so I will take him for a walk". They have poor auditory and reading comprehension, and fluent, but nonsensical, oral and written expression. Individuals with receptive<unk>  usually have great difficulty understanding the speech of both themselves and others and are, therefore, often unaware of their mistakes. Receptive language deficits usually arise from lesions in the posterior portion of the left hemisphere at or near Wernicke's area. It is often the result of trauma to the temporal region of the brain, specifically damage to Wernicke's area. Trauma can be the result from an array of problems, however it is most commonly seen as a result of stroke * Individuals with expressive<unk>  (Broca's<unk>  frequently speak short, meaningful phrases that are produced with great effort. It is thus characterized as a nonfluent<unk> . Affected people often omit small words such as "is", "and", and "the". For example, a person with expressive<unk>  may say, "walk dog", which could mean "I will take the dog for a walk", "you take the dog for a walk" or even "the dog walked out of the yard." Individuals with expressive<unk>  are able to understand the speech of others to varying degrees. Because of this, they are often aware of their difficulties and can become easily frustrated by their speaking problems. While Broca's<unk>  may appear to be solely an issue with language production, evidence suggests that it may be rooted in an inability to process syntactical information. Individuals with expressive<unk>  may have a speech automatism (also called recurring or recurrent utterance. These speech automatisms can be repeated lexical speech automatisms; e.g., modalisations ('I can't..., I can't...'), expletives/swearwords, numbers ('one two, one two') or non-lexical utterances made up of repeated, legal but meaningless, consonant-vowel syllables (e.g.., /tan tan/, /bi bi/). In severe cases, the individual may be able to utter only the same speech automatism each time they attempt speech. * Individuals with anomic<unk>  have difficulty with naming. People with this<unk>  may have difficulties naming certain words, linked by their grammatical type (e.g., difficulty naming verbs and not nouns) or by their semantic category (e.g., difficulty naming words relating to photography but nothing else) or a more general naming difficulty. People tend to produce grammatic, yet empty, speech. Auditory comprehension tends to be preserved. Anomic<unk>  is the<unk> l presentation of tumors in the language zone; it is the<unk> l presentation of Alzheimer's disease. Anomic<unk>  is the mildest form of<unk> , indicating a likely possibility for better recovery. * Individuals with transcortical sensory<unk> , in principle the most general and potentially among the most complex forms of<unk> , may have similar deficits as in receptive<unk> , but their repetition ability may remain intact. * Global<unk>  is considered a severe impairment in many language aspects since it impacts expressive and receptive language, reading, and writing. Despite these many deficits, there is evidence that has shown individuals benefited from speech language therapy. Even though individuals with global<unk>  will not become competent speakers, listeners, writers, or readers, goals can be created to improve the individual's quality of life. Individuals with global<unk>  usually respond well to treatment that includes personally relevant information, which is also important to consider for therapy. * Individuals with conduction<unk>  have deficits in the connections between the speech-comprehension and speech-production areas. This might be caused by damage to the arcuate fasciculus, the structure that transmits information between Wernicke's area and Broca's area. Similar symptoms, however, can be present after damage to the insula or to the auditory cortex. Auditory comprehension is near normal, and oral expression is fluent with occasional paraphasic errors. Paraphasic errors include phonemic/literal or semantic/verbal. Repetition ability is poor. Conduction and transcortical<unk> s are caused by damage to the white matter tracts. These<unk> s spare the cortex of the language centers but instead create a disconnection between them. Conduction<unk>  is caused by damage to the arcuate fasciculus. The arcuate fasciculus is a white matter tract that connects Broca's and Wernicke's areas. People with conduction<unk>  typically have good language comprehension, but poor speech repetition and mild difficulty with word retrieval and speech production. People with conduction<unk>  are typically aware of their errors. Two forms of conduction<unk>  have been described: reproduction conduction<unk>  (repetition of a single relatively unfamiliar multisyllabic word) and repetition conduction<unk>  (repetition of unconnected short familiar words * Transcortical<unk> s include transcortical motor<unk> , transcortical sensory<unk> , and mixed transcortical<unk> . People with transcortical motor<unk>  typically have intact comprehension and awareness of their errors, but poor word finding and speech production. People with transcortical sensory and mixed transcortical<unk>  have poor comprehension and unawareness of their errors. Despite poor comprehension and more severe deficits in some transcortical<unk> s, small studies have indicated that full recovery is possible for all types of transcortical<unk> . Classical-localizationist approaches Cortex Localizationist approaches aim to classify the<unk> s according to their major presenting characteristics and the regions of the brain that most probably gave rise to them. Inspired by the early work of nineteenth-century neurologists Paul Broca and Carl Wernicke, these approaches identify two major subtypes of<unk>  and several more minor subtypes: * Expressive<unk>  (also known as "motor<unk> " or "Broca's<unk> "), which is characterized by halted, fragmented, effortful speech, but well-preserved comprehension relative to expression. Damage is typically in the anterior portion of the left hemisphere, most notably Broca's area. Individuals with Broca's<unk>  often have right-sided weakness or paralysis of the arm and leg, because the left frontal lobe is also important for body movement, particularly on the right side. * Receptive<unk>  (also known as "sensory<unk> " or "Wernicke's<unk> "), which is characterized by fluent speech, but marked difficulties understanding words and sentences. Although fluent, the speech may lack in key substantive words (nouns, verbs, adjectives), and may contain incorrect words or even nonsense words. This subtype has been associated with damage to the posterior left temporal cortex, most notably Wernicke's area. These individuals usually have no body weakness, because their brain injury is not near the parts of the brain that control movement. * Conduction<unk> , where speech remains fluent, and comprehension is preserved, but the person may have disproportionate difficulty where repeating words or sentences. Damage typically involves the arcuate fasciculus and the left parietal region. * Transcortical motor<unk>  and transcortical sensory<unk> , which are similar to Broca's and Wernicke's<unk>  respectively, but the ability to repeat words and sentences is disproportionately preserved. Recent classification schemes adopting this approach, such as the Boston-Neoclassical Model, also group these classical<unk>  subtypes into two larger classes: the nonfluent<unk> s (which encompasses Broca's<unk>  and transcortical motor<unk>  and the fluent<unk> s (which encompasses Wernicke's<unk> , conduction<unk>  and transcortical sensory<unk> . These schemes also identify several further<unk>  subtypes, including: anomic<unk> , which
Aphasia
Visual impairment
Aphantasia
Ectopia 
Ophthalmia
Color blindness
Cortical blindness
Amblyopia