anti-

1.
a prefix meaning “against,” “opposite of,” “antiparticle of,” used in the formation of compound words (anticline); used freely in combination with elements of any origin (antibody; antifreeze; antiknock; antilepton).
Also, before a vowel, ant-.
Origin
Middle English < Latin < Greek, prefixal use of antí; akin to Sanskrit ánti opposite, Latin ante, Middle Dutch ende (> Dutch en and), English an- in answer. Cf. ante-, and
Can be confused
ante, ante-, anti-, auntie.
British Dictionary definitions for anti-

anti-

prefix
1.
against; opposing: anticlerical, antisocial
2.
opposite to: anticlimax, antimere
3.
rival; false: antipope
4.
counteracting, inhibiting, or neutralizing: antifreeze, antihistamine
5.
designating the antiparticle of the particle specified: antineutron
Word Origin
from Greek anti
Word Origin and History for anti-

word-forming element meaning "against, opposed to, opposite of, instead," from Old French anti- and directly from Latin anti-, from Greek anti "against, opposite, instead of," also used as a prefix, from PIE *anti "against," also "in front of" (see ante). It appears in some words in Middle English but was not commonly used in word formations until modern times.

anti- in Medicine

anti- or ant-
pref.

  1. Opposite: antimere.

  2. Opposing; against: antisocial.

  3. Counteracting; neutralizing: antibody.

anti- in Science
anti-  
A prefix whose basic meaning is "against." It is used to form adjectives that mean "counteracting" (such as antiseptic, preventing infection). It is also used to form nouns referring to substances that counteract other substances (such as antihistamine, a substance counteracting histamine), and nouns meaning "something that displays opposite, reverse, or inverse characteristics of something else" (such as anticyclone, a storm that circulates in the opposite direction from a cyclone). Before a vowel it becomes ant-, as in antacid.