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.

abiotrophy (s) (noun), abiotrophies (pl)
1. The loss of vitality in or the degeneration of certain cells or tissues, as in the aging process; physical degeneration; loss of vitality: The loss of functions or vitality in an organism or in cells or tissues which is not a result of any apparent injury; for example, senile dementia and related abiotrophies.
2. Progressive loss of vitality of certain tissues or organs leading to disorders or losses of functions: The abiotrophy of the heart may be appreciably shorter than that of other organs of the body which can lead to early disturbances in activities that upset other bodily organs.
ablepsia (s) (noun) (no plural)
1. Loss of sight; literally, "not seeing": A trained seeing eye dog is useful if a person suffers from ablepsia.
2. Blindness, unable to see: Because Dan's mother experienced ablepsia, she is using a white cane to help her get around safely in the community.
abrachia (s) (noun), abrachias (pl)
The congenital absence of arms or having no arms: Abrachia is an abnormal physical condition resulting from defective genes or developmental deficiencies.
abrachiocephalia, acephalobrachia (s) (noun); abrachiocephalias, acephalobrachias (pl)
A congenital absence of the head and arms or upper limbs: The veterinarian was puzzled by the birth of the pig that had been born with abrachiocephalia.

The acephalobrachia and the abrachiocephalia consist of humans that are missing heads and upper arms during fetal development and then at birth.

abranchiate (adjective) (not comparable)
Without gills; no gills: An example of an abranchiate mammal is a whale.
abrosia (s) (noun), abrosias (pl)
The total lack of food consumption; fasting (no food, not eating): The prison inmates organized a fasting campaign to emphasize the poor prison conditions and so they were participating in total ambrosias.
abulia, aboulia (s) (noun); abulie; aboulias (pl)
A disorder marked by the partial or total inability to make decisions: Byron was told that he had abulia, also known as aboulia. In other words, he had neither the willpower nor any "wish power" and so he wasn't able to decide what to do and not even capable of doing anything even if he wanted to.
abysm (s) (noun), abysms (pl)
1. Something without an underside; chasm: The deep canyon seemed to be an abysm because Jodi could not see the bottom.
2. Anything too deep for measurement: The well in the garden was an abysm because Daryl was unable to determine how deep it was.
3. An immeasurably profound depth or void: Verna's heart felt like an abysm or a bottomless pit of sadness after her boyfriend left her for another relationship.
abysmal (adjective), more abysmal, most abysmal
1. Immeasurably deep, severe, or extreme; fathomless: The depth of her sorrow was an abysmal situation and, as a result, she could find no expression except to cry.
2. Incapable of being measured or even understood; incomprehensible, inscrutable: Kristy felt like an abysmal failure because she couldn't remember how to spell the key word in the spelling contest.
3. Etymology: from the year 1656, formed in English from obsolete abysm, "bottomless gulf, greatest depths"; from Old French abisme, from Vulgar Latin abyssimus.
Profoundly or extremely bad.
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abysmally (adverb), more abysmally, most abysmally
Regarding how something is expressed in a terrible manner; very badly: Kirk's lack of manners abysmally reflected his upbringing and attendance at a lower level public school.
abyss (s) (noun), abysses (pl)
1. A bottomless pit: Jim leaned over the precipice and saw the deep abyss.
2. Anything too deep or too great to be measured; lowest depth: Melody's heart felt like an abyss of despair after she received the e-mail.
3. An immeasurably deep chasm, depth, or void: The canyon was described as an abyss because it was almost impossible to see its bottom.
4. The primeval chaos out of which it was believed that the earth and sky were formed: The film portrayed the abyss out of which the formation of the earth and solar system was supposed to have taken place.
5. The abode of evil spirits; thought of as a bottomless pit: Hugh's anguished soul descended into the abyss of hell.

Strictly speaking, the abyss is a particular zone extending between 3,000 and 6,000 meters (9,840 and 19,680 feet at 3.28 feet per meter) in depth. By extension, the abyss is also used to designate deep oceans everywhere.

abyssal (adjective), more abyssal, most abyssal
1. Pertaining to the depths of the ocean to which light does not penetrate; unfathomable: In order to explore the abyssal regions of the sea, specialized underwater robots were used.
2. In oceanography, of or relating to the deepest regions of the sea and to the organisms inhabiting that environment at depths between 4,000 and 6,000 meters (13,123 feet and 19,685 feet): The abyssal fishes appeared to be blind because there was no light where they lived.
abyssal-benthic (adjective) (not comparable)
In oceanography, of or relating to the deepest regions of the sea and the organisms inhabiting that environment: There was an article in Jim's newspaper reporting that a ship recently sank in the abyssal-benthic area of the Pacific Ocean near California and was completely inaccessible or unreachable.
abyssobenthic, abyssobenthonic (adjective); more abyssobenthic, more abyssobenthonic; most abyssobenthic, most abyssobenthonic
1. Pertaining to, or found on, the bottom of the sea at depths exceeding about 1,000 meters (3280.839 feet): Willard had to use specialized equipment to explore the abyssobenthic areas of the ocean.
2. Descriptive of an organism living on or in the ocean floor in the great depths of the oceans or lakes into which light does not penetrate; commonly used in oceanography of depths between 4,000 and 6,000 meters (13,123 and 19,685 feet): The fish that was discovered recently was an example of an abyssobenthonic creature.
abyssolith (s) (noun), abyssoliths (pl)
A large mass of intrusive igneous rock having an exposed surface area of more than forty square miles, with no apparent base or floor of older rock: In their oil research, the scientists described the abyssolith layers of rock in which the fossil fuel could be found.

The term abyssolith is part of the vocabulary used in the science of petrology.