a-, an-

(Greek: prefix; no, absence of, without, lack of; not)

These prefixes are normally used with elements of Greek origin, a- is used before consonants and an- is used before vowels.

It affects the meanings of hundreds of words.

There are too many words that use these prefix elements to list all of them on this site; however, there are significant examples listed in this and the other units where they exist.

aplastic (adjective), more aplastic, most aplastic
1. A reference to a part of the body that has defective development or growth: The aplastic organ had an incomplete development as in aplastic anemia which occurs when the bone marrow does not provide sufficient red and white blood cell production.
2. Materials that are not easily molded or formed: Wayne, the artist, was working with aplastic materials; such as, stone to create a statue.
apleuria (s) (noun), apleurias (pl)
At birth, the absence of one or more ribs: The apleuria of the child came about during its fetal (pre-birth) development.
apnea, apnoea (s) (noun); apneas, apnoeas (pl)
1. The temporary stopping of breathing that takes place in some newborns and in some adults while they are sleeping: Apnea disrupts Harriet's sleep or, sometimes, she wakes up completely or goes into a shallow level of sleep.

Apnea involves the cessation of breathing either temporarily for a few seconds to a minute or two or for a longer period, which can possibly cause someone to die.

Since breathing is an automatic process controlled by nerve impulses in the center of a brain stem to the muscles in the chest that regulate lung expansions and contractions, prolonged apneas can occur if the brain stem is damaged by a stroke, by a transient ischemic attack (symptoms of stroke lasting less than 24 hours), or by a head injury.

Prolonged apnea can also occur because of certain drugs or as the result of airway obstructions, usually by food, drink, vomit, or a small inhaled object.

2. In zoology, a decrease or a minimal breathing in hibernating animals: Natural apneas take place when animals have periods of dormant (sleep) inactivities which usually occurs in winter with certain rodents, bats, and some large carnivores; such as bears.
apneumia (s) (noun), apneumias (pl)
The absence of the lungs at birth: Dr. Dawson informed the mother that her baby was born dead because it had apneumia and so it was unable to breathe.
apodal (adjective) (not comparable)
1. Characteristic of being footless: Apodal features; such as, snakes and eels are all naturally without feet or foot-like appendages.
2. In medicine, the congenital absence of feet at birth: Unfortunately, there are some apodal people who have been born without feet or who are even legless.
apodia (s) (noun), apodias (pl)
Those who have a congenital absence of feet: Generally, apodias are born without feet.
apodous (adjective) (not comparable)
A descriptive term for someone who has no feet either by birth or because of some physical injury or some physical ailment: The apodous soldier lost his feet and lower legs when he stepped on a land mine (explosive) that was hidden below the surface of the ground.
apody (s) (noun), apodies (pl)
A living creature or human who has a congenital or inborn absence of a foot or feet: The veterinarian was surprised about one of the newborn puppies being born as an apody.

Teresa's child was born as an apody.

apraxia (s) (noun), apraxias (pl)
A loss of the ability to carry out familiar, purposeful movements even when there is no paralysis or other motor or sensory impairments: William experienced apraxia that included his inability to perform movements that are necessary to use objects properly, even when the names and purposes of the objects were known and understood.
aprosexia (s) (noun), aprosexias (pl)
The inability to maintain attention or to concentrate: Aprosexias are medical conditions that are common in certain organic situations that affect the brain and are involved in some psychiatric circumstances.

Aprosexia can be a result of overwhelming emotions that constantly interfere with a person's thought processes.

A patient may show excellent attentive capacities when special interests are involved; however, aprosexias may occur when certain situations unexpectedly come to mind.

—Composed from information provided by
Psychiatric Dictionary, Seventh Edition, by Robert Jean Campbell, M.D.;
Oxford University Press; New York; 1996; page 61.
aprosodia (s) (noun), aprosodias (pl)
The inability of a person to alter the sounds of the voice in tone or pitch when speaking: Aprosodias indicate difficulties in expressing the emotional aspects of language (motor aprosodia) and is diagnosed as a non-dominant frontal lobe disease of the brain resulting in a bland, colorless, or blunted (less vigorous) speaking.

There are other kinds of aprosodias that involve inappropriate emotional expressions and the inability to understand the emotional aspects of another person's speech (sensory aprosodia) which suggests damage in the non-dominant temporal area of the brain.

—Composed from information provided by
Psychiatric Dictionary, Seventh Edition, by Robert Jean Campbell, M.D.;
Oxford University Press; New York; 1996; page 61.
aprosody (s) (noun), aprosodies (pl)
Absence of emotional tones or accents and normal changes when speaking: The aprosodies of Matthew were diagnosed by a psychiatrist as consisting of speech disorders that were characterized by the absence of normal variations in pitch, loudness, intonations, and rhythms when he was talking.
apsychia (s) (noun), apsychias (pl)
The loss of consciousness: While Peter was watching TV, he suddenly fell over on the couch apparently as a result of apsychia.
apsychognosia (s) (noun), apsychognosias (pl)
Not being aware of one’s own personality or mental condition: Wayne, afflicted with apsychognosia, doesn't realize how other people react to his behavior nor can he recognize the outward bodily signs or attributes of other people and things.
apsychosis (s) (noun), apsychoses (pl)
Absence of mental functioning and particularly of thinking, as when in a stupor: When someone has apsychosis, even psychosis (a severe mental disorder in which the patient withdraws into an inner world of disorganized thinking and feeling) is not evident because that person is not completely conscious.