Prefixes: a- and an- of English words, 
 
Part 3 of 4.
 
anopia to asemasia
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.  
 
anopia: 
 Absence of sight; especially, when due to a structured defect in or absence of an eye (or eyes). 
anorchism: 
 Absence of the testes. 
anorexia, anorexic: 
 A lack or loss of appetite for food; no appetite (also, a shortened term for anorexia nervosa). 
anorgasmy: 
 1. Lack of sexual pleasure; inability to achieve orgasm. 
 
2. Failure or lack of experiencing an orgasm. 
anorthopia: 
 Distorted vision in which straight lines appear as curves or angles, and symmetry is incorrectly perceived; without correct vision. 
anorthosis: 
 Sexual impotence. 
anosmia, anosphresia: 
 Loss or absence of the sense of smell. 
anosognosia: 
 Ignorance of the presence of disease. 
anotia: 
 Congenital absence of one or both auricles of the ears. 
anoxemia: 
 Absence of oxygen in arterial blood. 
anoxia: 
 1. Absence or almost complete absence of oxygen from inspired gases, arterial blood, or tissues. 
 
2. Absence or deficiency of oxygen in body tissues. 
anuran: 
 A reference to frogs and toads, all of which have no tail (an- [without] + Greek oura [tail]) and are highly specialized for jumping. 
anuria, anuric: 
 Absence of urine formation. 
anypnia: 
 Sleeplessness. 
apancreatic: 
 Without a pancreas. 
aparalytic: 
 Without paralysis; not causing paralysis. 
apathy, apathetic: 
 1. Lack of emotion. 
 
2. Lack of interest; listless condition; unconcern; indifference. 
apellous: 
 Without skin. 
aphagia: 
 The inability to swallow; failure to eat or swallow because it causes pain. 
aphasia: 
 A defect or loss of expression by speech, writing, or signs, or of comprehending spoken or written language, due to injury or disease of the brain centers. 
aphilanthropy: 
 Lacking any concern or love for mankind. 
aphobic: 
 Without fear; fearless. 
aphonia: 
 A loss of voice due to an organic or functional disorder; voiceless, muteness. 
aphosphorosis: 
 A deficiency of dietary phosphorus in animals, particularly grazing cattle. 
aphotesthesia: 
 Decreased sensitivity of the retina to light caused by excessive exposure to sunlight. 
aphotic: 
 Without light; a reference to an environment or habitat having no sunlight of biologically significant intensity. 
aphototaxis, aphototactic: 
 The absence of a directed response to a light stimulus in a motile organism. 
aphototropism, aphototropic: 
 The absence of an orientation response to light. 
aphrasia: 
 1. The inability to utter or understand words connected in the form of phrases while the ability to understand, single words may be unimpaired; whereas groups of words forming phrases may baffle him/her completely as far as using or understanding them is concerned. 
 
2. Inability to speak, from any cause. 
aphydrotaxis, aphydrotactic: 
 The directed reaction of a motile organism away from moisture. 
aphyllous: 
 No leaves; lacking leaves, as most cacti. 
aplacental: 
 Without a placenta. 
aplasia: 
 1. Complete or partial failure of tissue to grow or develop; arrested development. 
 
2. Defective development or congenital absence of an organ or tissue. 
aplastic: 
 Without the power to grow toward normal, healthy tissue. 
apleuria: 
 Congenital absence of one or more ribs. 
apnea, apnoea: 
 1. Temporary stopping of breathing that occurs in some newborns and in some adults during sleep. 
 
2. Asphyxia. 
 
3. In zoology, a temporary suspension of breathing in hibernating animals. 
apneumia: 
 Congenital absence of the lungs. 
apodal, apodia: 
 Congenital absence of feet. 
apraxia: 
 A loss of the ability to carry out familiar, purposeful movement in the absence of paralysis or other motor or sensory impairments. 
aproctia: 
 Congenital absence or imperformation of the anus. 
aprosexia: 
 The inability to maintain attention. 
aprosodia: 
 The inability to inflect ones speech with affect or to recognize emotional elements of anothers speech. 
aprosody: 
 Absence, in speech, of the normal pitch, rhythm, and variations in stress. 
apsychia: 
 Loss of consciousness. 
apsychognosia: 
 A lack of awareness of ones own personality or mental state; used particularly to refer to the alcoholics typical lack of awareness of the outside worlds reaction to his drinking. 
apsychosis: 
 Absence of mental functioning and particularly of thinking, as when in a stupor. 
apterous: 
 1. Zoology, having no wings. 
 
2. Botany, having no winglike parts or extensions. 
apteryx: 
 Having no wings, wingless; the kiwi. 
aptyalism, aptyalia: 
 Deficiency or absence of saliva. 
apulmonism: 
 Absence of lungs. 
apyrexia, afebrile: 
 The absence or intermission of fever. 
apyrogenic: 
 Not caused by pus. 
arhinia, arrhina: 
 Congenital absence of the nose. 
arrhythmia: 
 Loss or abnormality of rhythm especially an irregularity of the heartbeat. 
aseism, aseismic: 
 No earthquake; without shaking (as exists with an earthquake). 
asemasia, asemia, asymbolia: 
 Aphasia with the inability to employ or to understand either speech or signs.
 
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