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.
2. An abnormal fear of falling or tripping: Ataxia is a lack of co-ordination in the muscles which is a symptom of damage to part of the central nervous system, and so people who have ataxiophobia may be that way because of their experiences in swaying or even falling down, especially if they close their eyes even for a second.
Atelesis has been used by psychiatrists to refer to three major disjunctions that are well known in schizophrenic psychopathology:
- Disjunction of a person's inner world and environment (autism or phantasies, delusions, hallucinations, etc.).
- Disjunction of one's ego and the contents of consciousness (splitting or incomplete ego development).
- Disjunction of someone's experience contents and the elementary forms of mental perception (destruction of conscious and willful focusing on one object or one component at a time).
2. Incomplete development which may refer to psychic infantilism or puerilism, and/or to physical dwarfism (microsomia): The unusual acting troupe consisted of people with atelioses; that is, they were dwarfish in stature but they were wonderful actors.
2. A person who denies, or disbelieves, that there is any such thing as a Supreme Being or beings: Joe's friend, even though he is an atheist, still enjoys having long philosophical discussions with the archbishop of the local church.
3. A disbeliever, an unbeliever, a nonbeliever, a denier of God's existence, a godless person: Laura believes in the existence of God, but her brother is an atheist and he thinks his sister is silly to believe that there is any such thing as a God.
4. Etymology: from French athéiste, from ancient Greek atheos, "godless, denying the gods"; from a-, "without, no" + theos, "god".

As an atheist, I proclaim that if there were a God, would people like this poor man be allowed to be in such miserable conditions? This is just one example of how so many people in the world are suffering and which proves to me that there is no God.
2. Related to or characterized by a denial that God exists or is real or present in any form: As a psychologist, Susan's atheistic beliefs contrasted with those of her college roommate who was a deeply devoted Christian.
2. Related to the absence of belief in a particular deity, pantheon, or religious doctrine: Lester, the archaeologist, was studying an ancient atheistical culture that apparently had no religious structure.
2. A reference to a nonexistent opening of a passage or entrance to heat or heat-rays: The athermic coating on the space shuttle proved to be successful when it re-entered the earth’s atmosphere.
3. Characterized by the absence of fever: After a worrisome night, baby Jill seemed to be athermic and now had a cool forehead and no fever.
4. Relating to being heatless: It was speculated that many of the planets in the solar system were of an athermic nature; that is, they had no natural heat.
2. Apathy, emotional indifference, or unresponsiveness: Because of Teresa's persisting athymia, Dr. Brown prescribed a mild antidepressant.
Priscilla's athymia was expressed by the fact that she didn't care if she got any better or not, nor whether she would live or die.
3. A congenital lack at birth of a thymus gland (an organ situated in the center of the upper chest just behind the breastbone that assists the immune system): Dr. Bowers noted that, given the athymia of her patient, a regimen of medications to counter the inherent immunodeficiency was necessary.There are those who become atokous by having their reproductive organs removed, either by choice or because they have genetically transmissible disabilities, etc.
Other atokous examples include making some plants incapable of bearing fruit or germinating, or the rendering of land that makes it unfruitful because of chemicals, excessive salt, etc.