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.

asiderosis (s) (noun), asideroses (pl)
An abnormal lack of a mineral reserve that is essential for proteins that stimulate chemical reactions and for the formation of red blood cells of the body: The patient's anemia, or decreased amount of red corpuscles in the blood, was caused by asiderosis and she needed to eat foods rich in iron to overcome her condition.
asitia (s) (noun), asitias (pl)
Having no appetite for food: Tom's asitia was an indication of his dislike of food or eating anything.

One reason for having asitia is when hunger has gone on for a long time regardless of what the reason was for the initial deprivation of food.

Asitia, or the destruction of the appetite for food, may come from starvation or severe malnutrition; as seen, in the poor, who can't afford to pay for adequate nourishment.

—The examples of asitia [anorexia, secondary mental] were partially compiled from
Psychiatric Dictionary, Seventh Edition by R.J. Campbell, M.D.;
Oxford University Press; New York; 1996; page 49.
asocial (adjective), more asocial, most asocial
1. Referring to the condition of being unable or unwilling to conform to normal standards of behavior with other people: Helena was a very asocial individual who always did what she wanted despite what was typically acceptable by others.
2. Pertaining to the inconsideration of others and more interested in oneself than in other people: Hector’s mother was always cautioning him not to be such an asocial person when he was playing with other children on the playground.
asoma, asomus (s) (noun); asomata (pl)
Having an incomplete body: Dr. Anderson, the obstetrician, who always provides medical care to women during pregnancy and childbirth, presented bad news to the pregnant woman as he told her that she had an unborn baby with an asoma, which is an incompletely developed and nonfunctional body with a deformed head and body.
asomatognosia (s) (noun), asomatognosias (pl)
1. Lack of awareness of the condition of all or part of a person's body: Gerard had an asomatognosia which meant that he didn't realize that his paralyzed arm belonged to him.
2. The inability of a person to recognize what is happening to parts of his or her body: Maggie had a condition of asomatognosia which made it impossible for her to realize what was happening to various parts of her body because of her impaired (mentally unfit) brain functions.
asomatophyte (s) (noun), asomatophytes (pl)
A plant in which there is no distinction between body and reproductive cells: For Ben's research project in botany, he was hoping to catalogue several examples of asomatophytes from the local park.
asphyxia (s) (noun), asphyxias (pl)
1. A stopping of the pulse because of pathological (disease or illness) changes that are caused by a lack of oxygen when breathing air, resulting in hypoxia and hypercapnia: Asphyxia is a condition in which there is an extreme decrease in the concentration of oxygen in the body that is accompanied by an increase in the concentration of carbon dioxide which can result in a loss of consciousness or even death.

Asphyxia can result from choking, drowning, electric shock, injury, or the breathing in of non-toxic or toxic gases.

2. Etymology: from Latin asphyxia, borrowed from Greek asphyxia, "a stopping of the pulse"; from a-, "without" + sphyxis, "pulse"; from sphyzein, "to throb", of uncertain origin.
asplenic (adjective) (not comparable)
A reference to the removal and absence of the spleen: The asplenic person is someone who no longer has the saclike mass of lymphoid tissue called the spleen that is normally located in the left upper quarter of the abdomen, just below the diaphragm and behind the stomach.

Asplenic people have lost an organ that performs important functions related to both the immune and the cardiovascular systems.

asporous (adjective) (not comparable)
A reference to having no true spores because of the inability to produce them: Asporous organisms (protozoa, fungi, and certain plants) are incapable of reproducing the elements necessary for reproduction.
astasia (s) (noun), astasias (pl)
Motor incoordination with the inability to stand up: Ben's astasia was caused by a sudden absence of his muscular timing or synchronization, possibly because of some kind of nerve damage.
astatic (adjective), more astatic, most astatic
Being unsteady and unstable: May's astatic condition made it impossible for her to walk or to stand without falling down.
asterixis (s) (noun), asterixes (pl)
A lack of or a lapse of posture consisting of momentary loss of a fixed position of the hands or arms followed by a jerking recovery movement that restores the limb to its original position; also known as "flapping tremor": Abnormal muscle tremor consisting of involuntary jerking of the hands is known as asterixis and it involves a shaking of the wrists and hands when the arms are extended and they are described as resembling a bird flapping its wings.
asthenia (s) (noun), asthenias (pl)
An abnormal lack or loss of strength and energy: Robert's asthenia showed his weakness and lack of vital forces which resulted in his having debility and feebleness.
asthenopia (s) (noun)
Eye weakness, or strain; often causing a headache, ocular discomfort, dimness of vision, etc.: Nigel's asthenia included such symptoms as fatigue, red eyes, eye strain, pain in or around the eyes, blurred vision, and occasional double vision.
asthenospheric (adjective), more asthenospheric, most asthenospheric
1. A reference to the zone beneath the earth's surface that lies beneath the lithosphere and consists of several hundred kilometers of weak material that readily yields to persistent stresses: According to the theory of plate tectonics, the Earth's lithosphere is a rigid outer layer that moves slowly over the weaker asthenospheric zone.
2. Etymology: from Greek astheneia, "weakness"; which consists of a-, "without" + sthenos, "strength" + -spheric, "being around" or "a zone".