Prefixes: a- and an- of English words, 
 
Part 4 of 4.
 
asemia to tritanopia
a-,  an- (Greek: a prefix meaning: 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 some significant examples listed in this and the other groups provided.  
 
asemia: 
 Loss of the ability, previously possessed, to make or understand any sign or token of communication, whether of organic or emotional origin. 
asepsis, aseptic: 
 1. A condition in which living pathogenic organisms are absent; a state of sterility. 
 
2. Free from microorganisms that produce disease, fermentation, or  putrefaction. 
asexual: 
 1. Reproduction without nuclear fusion in an organism. 
 
2. Having no sexual desire or interest. 
 
3. Having no sex; that is, genderless (neither male nor female). 
asiderosis: 
 An abnormal decrease of the iron reserve of the body. 
asitia: 
 Anorexia; no appetite for food. 
asocial: 
 Not social; indifferent to social values; without social meaning or significance. 
asoma: 
 Without a complete body; a fetus with only a rudimentary body. 
asomatognosia: 
 1. Lack of awareness of the condition of all or part of ones body. 
 
2. Lack of somatognosis which is a general feeling of the existence of ones body and of the functioning of the organs. 
asomatophyte: 
 A plant in which there is no distinction between body and reproductive cells. 
aspermia: 
 Failure of the formation or the emission of semen. 
asphyxia: 
 A stopping of the pulse; pathological changes caused by lack of oxygen in respired air, resulting in hypoxia and hypercapnia. 
asplenia, asplenic: 
 Absence of the spleen. 
asporous: 
 Having no true spores; applied to microorganisms. 
astasia, astatic: 
 Motor incoordination with an inability to stand. 
astereognosis: Tactile amnesia: 
 Loss or lack of the ability to understand the form and nature of objects that are touched (stereognosis), a form of tactile agnosia. 
asterixis: 
 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. 
asthenia, asthenic: 
 Lack or loss of strength and energy; weakness; debility or diminution of the vital forces. 
asthenopia: 
 Eye weakness or strain, often causing headache, ocular discomfort, etc. 
asthenosphere: 
 A zone beneath the earths surface that lies beneath the lithosphere and consists of several hundred kilometers of weak material that readily yields to persistent stresses. 
astomatous: 
 Having no mouth, as certain ciliates. 
astomia: 
 Congenital absence of the mouth. 
asyllabia: 
 A form of aphasia characterized by an inability to form or understand syllables, even while recognizing individual letters. 
asymbolia, asymboly: 
 The loss of power to comprehend the symbolic meaning of things such as words, figures, gestures, and signs. 
asymmetry: 
 A lack or absence of symmetry; dissimilarity in corresponding parts of organs on opposite sides of the body that are normally alike. 
asymphytous: 
 Separate or distinct; not grown together. 
asymptomatic: 
 Without symptoms; producing or causing no symptoms. 
asymptote: 
 A straight line that a curve continually approaches, but never meets, even if the curve is extended to infinity. 
asynchronism, asynchronous, asynchrony: 
 1. Operating at a rate determined by the system rather than at a regular rate of chronological time; without a fixed time pattern. 
 
2. Describing the relationship of two or more systems that run at their own rates and interact at unpredictable times. 
asyndesis: 
 A pattern of language in which words and phrases are juxtaposed without grammatical linkage; seen in schizophrenic and other mental disorders. 
asynechia: 
 Absence of continuity of structure. 
asynergy, asynergy, asynergic: 
 Lack of coordination among various muscle groups during the performance of complex movements, resulting in a loss of skill and speed. 
asynesia: 
 Profound mental dullness; stupidity. 
asyntaxia: 
 Lack of proper and orderly embryonic development. 
asystole, asystolia, asystolic: 
 Absence of a heartbeat. 
atactic: 
 A reference to muscle movements, irregular; lacking in coordination. 
atactilia: 
 Loss of the sense of touch. 
ataraxia, ataractic: 
 1. The absence of anxiety or confusion; imperturbability; untroubled calmness; inner harmony. 
 
2. A tranquilizer; having a tranquilizing or calming effect. 
ataxaphasia: 
 An inability to form phrases and sentences despite the ability to enunciate individual words. 
ataxia, atactic, atactiform:
 1. Absence or lack of order; lack of coordination.
 
2. The inability of someone to coordinate muscle activity during a 
 voluntary movement; irregularity of muscular action. 
ataxiadynamia: 
 Muscular weakness combined with incoordination. 
ataxophobia: 
 A mental dread of disorder or untididness. 
atectonic: 
 A reference to an event that occurs in the absence of widespread crustal deformations. 
atelesis: 
 Absence of integration or successful completion. 
atelia, ateliotic: 
 Imperfect or incomplete development. 
ateliosis: 
 Incomplete development which may refer to psychic infantilism or puerilism, to mental retardation, and/or to physical dwarfism (microsomia). 
atheism: 
 1. The belief that there is no God, or denial that God or gods exist. 
 
2. Godlessness. 
athermal: 
 Not warm; said of springs with water that is below 15 degrees Centigrade. 
athermanous: 
 Absorbing heat rays and not permitting them to pass. 
athermic: 
 Without fever or with no rise of temperature.  
athymia: 
 1. A name formerly given to absence of feeling or emotion, as seen in depression or the dysthymic disorder. 
 
2. Apathy, emotional indifference, or unresponsveness. 
 
3. Unconsciousness. 
atocia: 
 Sterility in the female. 
atokous: 
 Without offspring; non-reproductive; vegetative. 
atom: 
 1. Literally, not cutable, not divisible. 
 
2. Originally, any of the indivisible particles postulated by philosophers as the basic component of all matter. 
 
3. A tiny particle of anything; jot. 
atonia: 
 Lack of tone or tension with reference to the muscles or bodily organs, etc. 
atonic: 
 Relating to or characterized by lack of tone or vital energy. It refers to the whole body, to a particular system of the body, or to single organs; especially to contractile organs. 
atony: 
 Lack of normal tone (tension) or strength (in muscles, etc.). 
atopognosis: 
 The inability to locate a sensation properly; sensory inattention. 
atoxic: 
 Not toxic; not caused by or associated with a toxin (poison). 
atraumatic: 
 Not inflicting or causing damage or injury. 
atrichous: 
 The absence of hair either congenital or acquired. 
atrophia: 
 The wasting away of tissues, organs, or the entire body. 
atrophy: 
 A wasting away, especially of body tissue, an organ, etc., or the failure of an organ or part to grow or develop, as with insufficient nutrition. 
avascular: 
 Without blood or lymphatic vassels. 
avirulence: 
 Not virulent. 
axenic: 
 Not contaminated by or associated with any foreign organisms, used in reference to pure cultures of microorganisms or to germ-free animals. 
aypnia: 
 Insomnia, sleeplessness. 
azoic: 
 1. Devoid of living organisms. 
 
2. Without life; specifically, designating or of the Early Precambrian (Archean) era, before life appeared on earth. 
azoospermia: 
 Absence of living spermatozoa in the semen. 
azygous: 
 Not occurring as one of a pair; having no mate, single. 
deuteranopia: 
 A visual defect in which the retina fails to respond to the color green; so named from blindness to the color green, which is regarded as the second primary color. 
myasthenia: 
 Abnormal muscle fatigue or weakness. 
neurasthenia: 
 A disorder originally thought to result from neural exhaustion, including such symptoms as chronic fatigue, weakness, and irritability. 
protanopia: 
 A visual defect in which the retina fails to respond to the color red; so named from blindness to the color red, which is regarded as the first of the primary colors. 
tritanopia: 
 A visual defect in which the retina fails to respond to the color blue; so named from blindness to the color blue, which is regarded as the third primary color.
 
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