Aphasia (also refered to as dysphasia) is a disorder of language, where a person's ability to use language to communicate is impaired in some way. Language functions which may be affected include talking, understanding, listening, writing, or doing mathematical calculations. Aphasia may occur after a brain injury (e.g. stroke), particularly if the brain injury affects the left side of the brain. Expressive Aphasia Expressive aphasia is a difficulty in putting words together to form a meaningful message. This may include such difficulties as: trouble thinking of specific words and names, difficulty putting words together into a sentence to describe ideas or thoughts, tending to repeat words, saying words that do not make sense, and difficulty writing words and sentences. The severity of these difficulties varies considerably for each person. Receptive Aphasia Receptive aphasia is a difficulty in comprehension of language, where the person cannot attach meaning to incoming words they hear or read. This difficulty can be especially noticable if a person is tired, or when the conversation is complex.

Apraxia is a disorder of speech (speech is the process of pronunciation and articulation) in which the difficulty involves planning, sequencing, and producing the movements required to make sounds and words. Verbal apraxia in particular refers to the ability to programme the lips and tongue in order to make muscle movements for speech, whereas oral apraxia refers to nonspeech movements of the lips and tongue such as blowing and puckering the lips. Apraxia therefore is often described as a problem with making the voluntary movements necessary for speech.

Dysarthria is a disorder of speech (speech is the process of pronunciation and articulation). After a brain injury (such as stroke, or a progressive neurological condition such as Parkinson's Disease or Huntington's Disease), the muscles of the mouth, face, voice box and respiratory system may become weak, move slowly or move differently, or not move at all. The speech condition that results is called dysarthria. The type and severity of dysarthria depends on the type of brain damage. Symptoms of dysarthria may include slurred sounding speech, a slow rate of speech, breathiness, drooling or poor control of saliva, and limited tongue, lip, and jaw movement.

Dysphagia is any problem in which the action of swallowing is either difficult to perform, painful, or swallowed material is disrupted somewhere in the passage from the mouth to the stomach. Dysphagia may be caused by an anatomical problem (e.g. cancer) or a neurological problem (e.g. after a stroke). Dysphagia may also occur as a result of impaired control of swallowing for other reasons (e.g. as a result of breathing difficulties, or when a patient is very frail).