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.

anacoustic zone; zone of silence (s) (noun); anacoustic zones; zones of silence (pl)
An area in outer space where sound cannot be transmitted: The anacoustic zone is said to be the upper portion of the earth's atmosphere starting at a hundred miles (160 kilometers) and on into interplanetary space, where sound cannot be projected because gas molecules are too far apart to serve as a transferring medium.

The anacoustic zone is also known as the "zone of silence".

anadenia (s) (noun), anadenias (pl)
Absence of glands or the temporary lack of glandular functions: Brooke’s stomach difficulties appeared to be related to chronic anadenia which resulted when her body had deficient glandular secretions.
anaerobic (adjective), more anaerobic, most anaerobic
1. Having to do with or occurring in the absence of atmospheric oxygen or air: Anaerobic digestion occurs when natural food stuffs decompose in the absence of oxygen and the result of this process is methane.
2. Relating to living or growing where there is no atmospheric oxygen: There are many investigative projects undertaken to study the possibilities of anaerobic farming in space.

Anaerobic bacteria get their oxygen by decomposing compounds containing oxygen.

anaerophyte (s) (noun), anaerophytes (pl)
A plant that grows without air: The scientists were enthusiastic about the discovery of an anaerophyte because of the possibilities of farming in outer space.
anaeroplasty (s) (noun), anaeroplasties (pl)
Treatment of wounds with the exclusion of air: The doctor decided to treat Saul's wound using the anaeroplasty method to seal the wound from any air so that it would heal faster and better.
anaesthesia, anesthesia (s) (noun); anaesthesias, anesthesias (pl)
A partial or complete loss of sensation, with or without the loss of consciousness; as a result of disease, injury, or the administration of a painkilling agent; usually by injection, inhalation, or hypnosis: Although anesthesia is used to eliminate tactile sensibility, or of any of the other senses, it refers especially to the absence of pain, because it is induced to permit the performance of surgery or other painful procedures.

Local anesthesia affects a limited area of the body; as opposed to general anesthesia, which affects the whole body.

Arrow pointing to words and info sections The index of anesthesia history, Parts 1, 2, and 3.

analgesia (s) (noun), analgesias (pl)
A state in which painful stimuli are so moderated that, though still perceived, they are no longer painful; and so there is no feeling of pain: Rosemarie was grateful for the medication which induced a state of analgesia because now she was not aware of any significant pain.
analgesic (s) (noun), analgesics (pl)
1. Compounds capable of relieving pain without the loss of consciousness or without producing anesthesia: Dr. Lawson injected Randal with a powerful analgesic so she could drill the decayed tooth without causing him any pain.
2. Those drugs that primarily relieve pain without blocking nerve-impulse conduction or markedly altering sensory functions: The new analgesic which Dr. Jones used was exceptional in terms of relieving or reducing Desiree's severe pain.
analphabetic (adjective), more analphabetic, most analphabetic
A reference to the inability to read or to write: Mrs. Nelson was concerned about the analphabetic state of some of her students and so she created special lessons for them.
anandria (s) (noun), anandrias (pl)
A loss or absence of masculinity: There were some associates who thought Elbert’s apparent anandria was a result of his lack of interest in any sports either as a participant or as an observer.
ananthous (adjective), more ananthous, most ananthous
In botany, having no flowers: Ernestine has a very interesting ananthous plant in her garden which has an abundance of leaves but no blossoms.
anaphrodisia (s) (noun), anaphrodisias (pl)
Repressing or destroying sexual desire: A side effect of the strong medication resulted in a condition of anaphrodisia.
anaphrodisiac (adjective), more anaphrodisiac, most anaphrodisiac
Relating to something which decreases sexual desires: In order to safely transport the stallion with the other horses, John, the veterinarian, gave him an anaphrodisiac injection.
anaptic (adjective), more anaptic, most anaptic
Pertaining to suffering that has no sense of touch or is characterized by tactile anesthesia: As a result of Elena's severe injuries, she lived as an anaptic person who could not feel anything.
anarchic (adjective), more anarchic, most anarchic
1. Showing no respect for established laws, rules, institutions, or authority: The anarchic mob was completely out of control and tried to destroy the bank.
2. Characterized by a lack of organization or control: The herd of wild ponies raced around in an anarchic manner, trying to escape from the corral.
3. Likely to cause the overthrow of a formal system of government or a breakdown of law and order: The rioters had anarchic objectives which were to create havoc and disruption in the city.