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.

apellous (adjective), more apellous, most apellous
1. Pertaining to a cut or severe scrape on the body that has caused the removal of skin: The nurse cleaned the apellous wound on Rita's leg before Dr. Jones started to treat the injury.
2. Being without skin: Olivia was preparing a meal with apellous chicken breast.
aphagia (s) (noun), aphagias (pl)
1. Abstention from eating: The prisoner announced that he was beginning an aphagia to protest his imprisonment and was refusing to eat.
2. The inability to swallow or failure to eat or swallow because it causes too much pain: Because of an injury to her throat, Tracy was experiencing severe aphagia and was unable to swallow food or liquids.
aphakia (s) (noun), aphakias (pl)
The absence of the crystalline lens: A cataract is an eye disease in which the lens or capsule of one or both eyes results in aphakia which is the removal of one or both lenses because cataracts decrease clear vision or even cause blindness.
aphasia (s) (noun), aphasias (pl)
A defect or loss of expression by speech, writing, signs, or of comprehending spoken or written language, as a result of injury or disease of the brain centers: Dr. Thompson, the new doctor at the speech clinic, specialized in working with clients who were suffering from aphasia.

Both survivors of the industrial explosion suffered aphasia and were unable to communicate to others or even to understand what was being communicated to them.

aphobic (adjective), more aphobic, most aphobic
Characteristic of being without fear; fearless: Mr. Anderson, the author, described the hero as a brave and aphobic man, willing to face any peril.
aphonia (s) (noun), aphonias (pl)
1. The inability of the larynx to produce normal speech or singing sounds: Because of the excessive use of her voice in various operas, Natasha experienced aphonia and was unable to continue her career.
2. A loss of a person's voice that can be caused by overuse, disease, or because of psychological reasons; such as hysteria: Meg experienced aphonias on several occasions as a result of her hysterias or neurotic disorders that were characterized by violent emotional outbreaks.
aphosphorosis (s) (noun), aphosphorose (pl)
A deficiency of an essential dietary element in animal diets which results in a lack of a major component of bones and other parts of the body: Aphosphorosis has a negative affect on one of the primary energy sources of the body because of an inadequate amount of phosphorus in the blood, muscles, nerves, and teeth.

Dr. George's diagnosis of the farmer's ill cattle was that they were suffering from aphosphoroses and required dietary supplements.

aphotesthesia (s) (noun), aphotesthesias (pl)
A physical condition that is caused by excessive exposure to sunlight: Aphotesthesia is characterized by a reduced retina sensitivity of the eyes to light.

The retinas are the areas at the back of a person's eyes which send light signals to the brain and where those signals are changed into images that may result in aphotesthesia when they are overexposed to sunlight.

aphotic (adjective), more aphotic, most aphotic
1. A description of those parts of the ocean that are not reached by sunlight, or plants that grow there without synthesizing light: The remote controlled camera was able to explore the aphotic depths of the ocean, looking for rare life forms.
2. A reference to any environment or habitat that has no sunlight of any biological significant intensity: The fish that lived for a long time in the dark cave evolved into a state of blindness because of their aphotic environment.
3. Etymology: from Greek a-, "not, without" + phos, "light"; literally, "no light".
aphototactic (adjective), more aphototactic, most aphototactic
Descriptive of organisms that don't respond to light: During biological experiments with phototropism of growing plants that normally bend toward light, biologists covered the tips of some seedlings with lightproof collars and they discovered that they became aphototactic plants because they wouldn't bend toward the light.

When the tips of the seedlings were covered with transparent collars or when lightproof collars were put below the tips, the seedlings bent toward the light and so they did not become aphototactic plants.

In his later years, Charles Darwin became increasingly interested in the study of plants. In 1881, he and his son, Francis, published a book called The Power of Movement in Plants, in which they reported their systematic experiments regarding the way in which growing plants bend toward light, a process known as phototropism.

—Compiled from information located in
The Living World, Second Edition, by George B. Johnson;
Washington University, St. Louis, Missouri;
McGraw-Hill Companies, Inc.; 2000; page 399.
aphototaxis (s) (noun), aphototaxes (pl)
The absence of any response to a light stimulus by an organism that can move: The aphototaxis of organisms is a condition that is characterized by their failure to react to light; neither moving toward the source of light (positive phototaxis) nor away from it (negative phototaxis).
aphrasia (s) (noun), aphrasias (pl)
1. The inability to utter or to understand short phrases (groups of words) that are spoken while still being able to understand or to speak single words: In conversation with people experiencing aphrasia, the listener may find it difficult to follow the conversation as the speaker may only be able to utter or understand single words, not phrases or sentences.
2. The inability to speak for any cause or reason: Phil has been afflicted with aphrasia and so he refuses to speak and sometimes he even loses the ability to talk.
aphrasic (adjective), more aphrasic, most aphrasic
A reference to someone who can't talk or use words that are normally combined or joined with other words: As a result of some disease, the aphrasic patient was unable to express himself with sentences that could usually be understood and sometimes he even refused to make an effort to do it.
aphyllous (adjective), more aphyllous, most aphyllous
Lacking or having no leaves: Cacti are the most common aphyllous plants known.

Since aphyllous plants don't have leaves, they perform photosynthesis in their stems and branches.

aplasia (s) (noun), aplasias (pl)
The complete or partial failure of tissue to grow or to develop; arrested or abnormal development: Aplasia is the defective development, or congenital (present at birth) absence, of an organ or tissue.

Dr. Lawson was discussing the aplasia of a localized area of the skin on Tina's scalp which was covered by a thin, almost transparent membrane.