a-, an- +

(Greek: a prefix meaning: 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.

akinesia, akinesis

1. Absence or poverty of movements.
2. Absence or diminution of voluntary motion that may range from moderate inactivity to almost complete immobility.

alalia

Speechlessness; loss of the ability to talk.

aleukemia

A lack of leukocytes in the blood.

aleukocytic

Absence or extremely reduced numbers of leukocytes in the blood or in lesions.

alexia

1. A loss of the ability to understand written language, inability to read because of brain lesions; word blindness.
2. An acquired disorder in reading ability; to be differentiated from dyslexia, which is a developmental problem in reading.

Strictly speaking, lexus and its derivatives refer to speech, not reading, because they are based on the Greek verb legein, "to speak", and not on the Latin verb legere, "to read". Current usage appears to reflect an etymological error, that has been accepted for so long that to insist on correcting it would be useless.

—Psychiatric Dictionary, 7th Ed., Robert J. Campbell, M.D.;
Oxford University Press, 1996; New York.

alogia

The inability to speak due to a mental deficiency or an episode of dementia.

amaranth

1. A legendary flower that never fades or dies.
2. Any plant of the genus Amaranthus, some of which are grown especially for their flowers and colored leaves.
3. Any of various annuals of the genus Amaranthus having dense green or reddish clusters of tiny flowers and including several weeds, ornamentals, and food plants. Also called "pigweed".
4. A deep reddish purple to dark or grayish, purplish red.
5. A dark red to purple azo dye.

amastia

Absence of the breasts.

amaurosis

Partial or total loss of sight.

ambrosia

1. In Greek and Roman mythology, the food or drink of the gods thought to bestow immortality.
2. Something especially delicious to taste or smell.
3. A fruit dessert made of oranges and shredded coconut and sometimes pineapple.
4. Etymology: borrowed perhaps through Middle French ambroysie, or directly from Latin ambrosia, from Greek ambrosia, feminine of ambrosios of the immortals; that is, gods, from ambrotos, "immortal" (a-, "not" + Greek brotos, "mortal" [from earlier mrotos] + -ia, a suffix that forms nouns).

amenorrhea

Absence or abnormal stoppage of the menses (menstruation); also amenia.

amentia

1. Without normal mental abilities; such as, a congenital mental deficiency or mental retardation.
2. Mental disorder characterized by confusion, disorientation, and occasionally stupor.
3. Subnormal development of the mind, with particular reference to intellectual capacities; a type of severe mental retardation.

ametria

Absence of the uterus.

amicrobic

Not microbic.

amicroscopic

Too small to be seen through a microscope; unable to be seen even with a microscope.