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.

adromia (s) (noun), adromias (pl)
The absence of an impulse conduction in a nerve of a muscle: Adromias are failures of muscle innervations or the lack of distributions of nerve fibers to organs or body regions.
adynamia (s) (noun), adynamias (pl)
1. Lack or loss of normal or vital powers: After the accident, Doreen felt a sense of adynamia overcome her and she fainted.
2. Characterized by or causing weakness: The combination of hot weather, and Mona's not feeling well, caused adynamia; so, she had to sit down.
adynamic (adjective), more adynamic, most adynamic
A reference to the lack of strength or vigor: Marty had an adynamic condition that reflected his absence of physical strength usually because of the illness he had experienced.
adytum (s) (noun), adyta (pl)
1. The sanctum in certain ancient temples which was available just for priests: Only the most holy of rites were conducted by the religious ministers in the adyta of ancient temples.
2. A private area or locality : During the court adjournment, the judge went to his adytum for a little rest.
3. Etymology: from Greek a-, "not" plus Greek dyein, "to enter".
afebrile (adjective), more afebrile, most afebrile
1. Relating to being without a fever: After a good night's sleep, Lora woke up rested with an afebrile feeling.
2. Unaccompanied by fever: Paulette's illness puzzled the doctors because, although she felt ill, she was afebrile.
3. Not feverish: Diana's brow felt afebrile and so her mother decided that her daughter no longer had a fever.
afetal (adjective) (not comparable)
Pertaining to the absence of a fetus, or not having an unborn child, by the end of the eighth week after conception to the moment of birth: The doctor told Estelle that she still had an afetal condition and so she was lacking a baby inside her womb.
agalactia (s) (noun), agalactias (pl)
Absence of milk in the breasts after childbirth: Although her child was just born, Nadine still had agalactia or a condition in which no milk was being secreted in her breasts.
agamic (adjective) (not comparative)
1. A reference to nonsexual reproduction, as by fission, budding, etc.: Some species reproduce without sexual unions or by germinating without impregnation; such as, agamic or unfertilized eggs.
2. A reference to organisms in which all individuals reproduce asexually: Agamic sponges can reproduce by simply fragmenting their bodies and each small portion grows and produces to a new sponge.

In agamic reproduction, the offspring are usually genetically identical to their parents.

Most of unicellular yeast-fungi result from agamic reproduction that takes place by cell fission or the formation of a small cell from a part of a larger one.

agamous (adjective) (not comparative)
Characteristic of not involving the fusion of male and female gametes in reproduction: Agamous male or female cells do not unite with cells of the opposite sex to produce zygotes which are the fertilized eggs that have only just started developing and are not yet embryos which can develop into embryos and then babies.
agamy (s) (noun), agamies (pl)
1. Absence or nonrecognition of the marriage relation or no marriage: There are some people who believe in agamy which is the rejection of any requirement that marriage is necessary.
2. In biology, having no distinguishable sexual organs; asexual: There are species of agamy that reproduce by the process in which a cell divides into two or more parts.
3. In botany, a reference to all flowerless and seedless plants that reproduce by means of spores: The agamies of plants consist of ferns and algae which do not bear flowers or seeds but reproduce with the scattering of cells that propagate or develop new organisms.
agastria (s) (noun), agastrias (pl)
Absence of a stomach: Agastria is a term that designates certain organisms which have no proper digestive cavities or stomachs.
agastric (adjective), more agastric, most agastric
A descriptive term indicating species that have no alimentary canals: There are agastric creatures that do not have a tubular passage which functions in digestion and elimination.
agenesis (s) (noun), ageneses (pl)
A lack of development or absence of an organ or other body part: From time to time, a child is born with agenesis and so it may have an undeveloped or a missing body part.
ageotropism (s) (noun), ageotropisms (pl)
1. The absence of orientation movements in response to gravity: When participating in a space flight simulator, the astronaut experienced ageotropism and so he had no sense of responding to gravity.
2. Turning away from the earth: Elena was studying plant ageotropism and so she was growing plants in a gravity-free environment.
3. A part of a plant that would be expected to grow as gravity pulls it down, but instead grows upward, such as the knee roots of cypress trees: Marcella tripped over the ageotropisms of the tree in the swamp because the roots were sticking up out of the earth.
ageusia (uh GYOO see uh), ageustia (uh GYOOS tia) (s) (noun); ageusias, ageustias (pl)
Absence or impairment of the sense of taste; it may be a result of a disorder in the gustatory apparatus (i.e. the taste buds): Ageusia is the inability to taste sweet, sour, bitter, or salty substances.

Ageusias may be seen in psychiatric conditions, particularly in depressed patients who complain that food is tasteless.