"Aphasia" is a language impairment caused by damage to the areas of the brain responsible for language function. Damage to the brain can be caused by stroke, tumour or head injury. Different aspects of language can be affected to varying degrees depending on the location and severity of the damage.
For most people, language function occurs in the left hemisphere of the brain. Damage to Broca's area, a region in the frontal loble of the left hemisphere, results in expressive aphasia (Broca's aphasia). This causes an impairment in the ability to produce language. Damage to Wernicke's area, a region in the left temporal lobe, results in receptive aphasia, or Wernicke's aphasia. This impairs one's ability to understand language. Things are not usually so clear-cut in reality. Individual differences in brain function and differences in location and spread of damage means that impairment is unique to the individual.

There are some general symptoms aphasic individuals can experience. Word finding difficulties, or anomia, can be frustrating and slow down communicaiton. Some people try to work around word finding diffficulty by giving descriptions or definitions or talking around their difficulties. This is called circumloction.

A person with aphasia might use an incorrect word or unrecognizable word in place of the target word. This is a paraphasia. Paraphasias can be classified in 3 types. Phonemic or literal paraphasias are word errors that sound very close to the intended word (e.g., coke for coat). A verbal or semantic paraphasia occurs when a word that is related in meaning to the target word is substituted (e.g., plum for peach). The third type of paraphasia is a neologism - an invented word that is not recognizable as a word in the speaker's language.

Repetition of a word or phrase when it is no longer appropriate is "perseveration". The individiual seems to get stuck in a pattern of response and cannot break out of it.

When speaking with a person who has aphasia, it helps to minimize distractions, speak slowly and clearly. If they have comprehension difficulties, use short simple sentences and pause between sentences. Pair gestures with your speech to aid comprehension. Allow them more time to respond. If you need to find out information, ask questions that can be answered easily with a yes or no or other single word. Remember that a person with aphasia has not lost their intelligence, they just have difficulty communicating.