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.

astomatous (adjective) (not comparable)
Characteristic of having no mouth nor mouthlike opening, as certain ciliates: The microscopic hairs of the automatous protozoan stirred the water, enabling it to absorb food without having a mouth or mouth-like structure.
astomia (s) (adjective) (not comparable)
A reference to congenital absence of the mouth: Sadly, Fay's baby was born without a mouth.
asyllabia (s) (noun), asyllabias (pl)
A form of aphasia (brain damage) characterized by an inability to form or to understand syllables, even while recognizing individual letters: Although Max was able to recognize individual letters, he could not understand or use them in words because he suffered from asyllabia.
asymbolia (s) (noun), asymbolias (pl)
The loss of the ability to comprehend the symbolic meanings of things; such as, words, figures, gestures, and signs: Harry's asymbolia made him incapable of understanding previously familiar symbols and signs; usually, because of a lesion in his brain which is a pathological or traumatic damage of brain tissue.
asymboly (s) (noun), asymbolies (pl)
The inability to understand or to interpret words, numbers, gestures, signs, diagrams, musical notes, or even occasionally other sensory information: Some people have asymbolies that make it impossible for them to actively communicate or to perceive what is being presented to them in written forms or symbols.
asymmetry (s) (noun), asymmetries (pl)
A lack or absence of parts that are the same or similar in form or structure: When Dr. Spock checked the X-ray, he was surprised to see the asymmetry of the corresponding parts of body organs that were on the opposite sides of Steven's body which were normally alike.
asymphytous (adjective), more asymphytous, most asymphytous
Pertaining to being separate or distinct; not grown together: The toes of the rare specimen were asymphytous and therefore it was unable to swim.
asymptomatic (adjective), more asymptomatic, most asymptomatic
Without any sensations or having no changes in bodily functions that are experienced by a patient and is associated with a particular disease: After several physical examinations, the doctor determined that Mildred had no asymptomatic indications of any ailments.
asymptote (s) (noun), asymptotes (pl)
1. A straight line that a curve continually approaches, but never meets, even if the curve is extended to infinity: In a classic picture illustrating perspective, the parallel rails of a railroad are asymptote in that they never intersect.
2. Etymology: from Greek asymptotos, "not falling together", from a-, "not" + syn "with" + ptotos, "fallen"; from piptein, "to fall".
asynchronism (s) (noun), asynchronisms (pl)
1. Relating to something that is operating at a rate determined by the system rather than at a regular rate of chronological time; without a fixed time pattern: The injection of the new medication was supposed to correct the asynchronism of Kim's nerve impulses.
2. Describing the relationship of two or more systems that run at their own rates and interact at unpredictable times: Despite practicing for weeks, Sharon's jumping jack, or toy figure of a man with jointed limbs that could be moved by pulling attached strings, appeared to be resulting in asynchronisms or uncoordinated movements.
asynchronous (adjective), more asynchronous, most asynchronous
Relating to something that does not occur nor exist at the same time: The use of asynchronous e-mails is an advantage over telephone calls because responses can take place whenever it's convenient so they don't all have to be done at the same time.

The tourists noticed that their watches were asynchronous so they synchronized them so they could return to the bus at the appointed time for the return trip to the hotel.

asynchrony (s) (noun), asynchronies (pl)
A situation in which things don't happen, move, or exist at the same time: The express way had traffic for several days that the police considered to be an example of asynchrony because it was not as normal as it usually is during the week days.
asyndesis (s) (noun), asyndeses (pl)
A pattern of language in which words and phrases are juxtaposed without grammatical linkage as seen in schizophrenic and other mental disorders: The asyndesis of the readings that Charlene presented to the doctor was a language that seemed to be disjointed and disconnected.

One of Dr. Smith's patients was asked what caused the wind to blow, and Marge said that the wind was a result of velocity, the loss of air, evaporations of water, contact with trees, and of air in the trees; all of which indicated a case of asyndesis.

asynechia (s) (noun), asynechias (pl)
Absence of continuity of a structure: The asynechia of the body part and tissues of the wounded soldier's abdominal area presented medical problems that were almost impossible for the army medics to solve.
asynergia (s) (noun), asynergias (pl)
An absence of harmonious and coordinated movements between muscles having opposite actions: The synergies of the flexors and extensors of Peg's arm joints indicated a disease of the nervous system.