Prefix
A prefix is an affix which is placed before the stem of a word. Particularly in the study of languages, a prefix is also called a preformative, because it alters the form of the word to which it is affixed.
Prefixes, like other affixes, can be either inflectional, creating a new form of a word with the same basic meaning and same lexical category, or derivational, creating a new word with a new semantic meaning and sometimes also a different lexical category. Prefixes, like all affixes, are usually bound morphemes.
English has no inflectional prefixes, using only suffixes for that purpose. Adding a prefix to the beginning of an English word changes it to a different word. For example, when the prefix un- is added to the word happy, it creates the word unhappy.
The word prefix is itself made up of the stem fix, and the prefix pre-, both of which are derived from Latin roots.
English language
List of English derivational prefixes
This is a fairly comprehensive, although not exhaustive, list of derivational prefixes in English. Depending on precisely how one defines a derivational prefix, some of the neoclassical combining forms may or may not qualify for inclusion in such a list. This list takes the broad view that acro- and auto- count as English derivational prefixes because they function the same way like that of prefixes such as over- and self- do.As for numeral prefixes, only the most common members of that class are included here. There is a large separate table covering them all at Numeral prefix > Table of number prefixes in English.
| Prefix | Meaning | Example | Comments |
| a- | "not" | asymmetric, "not symmetric" | takes the form an- before vowels; see privative alpha |
| acro- | "high" | acrophobia, "fear of heights" | |
| allo- | "other" | allotransplantation, "transplant of tissue from another person" | |
| alter- | "other" | alter ego, "other personality" | |
| ante- | "prior" | antebellum, "before a war" | |
| anti- | "opposite" | anti-inflammatory, "against inflammation" | |
| auto- | "by oneself or itself" | automobile, "moves itself" | |
| bi- | "two" | bicentennial, "consisting of or occurring every two centuries" binomial, "two terms" | See number prefixes in English |
| co- | "together" | cooperation, "working together" | takes the form con- before vowels |
| cis- | "on the same side" | cisgenesis, "genes don't change within breeding and birth setting" | |
| contra- | "below" ; "against" | contraindication, "against indication" | |
| counter- | "against" | countermeasure, "action against" | |
| de- | "negative, remove" | deactivate, "stop from working" | |
| di- | "two" | diatomic, "two atoms" dipole, "two poles" | See number prefixes in English |
| dis- | "negative, remove" | disappear, "vanish" | |
| down- | "down"; "reduce" | downshift, "shift to a lower gear" downregulation, "regulation toward lessened expression" | |
| dys- | "negative, badly, wrongly" | dysfunction, "bad function" | |
| epi- | "upon addition", "above" | epidural, "outside the dura mater" | |
| extra- | "to a greater extent" ; "beyond" | extracellular, "outside a cell" | |
| fore- | "before" | foresight, "seeing beforehand" | |
| hemi- | "half" | hemisphere, "half of a sphere" | See number prefixes in English |
| hexa- | "six" | hexagon, "six-sided polygon" | See number prefixes in English |
| hyper- | "beyond" | hypercalcemia, "too much calcium in the blood" | See hyper |
| hypo- | "marginal"; "not enough" | hypokalemia, "not enough potassium in the blood" | |
| ig- | "not" | ignoble, "not noble" ignorant, "not knowing" | ig-, il-, im-, in-, or ir- |
| il- | "not" | illegal, "not legal" | ig-, il-, im-, in-, or ir- |
| im- | "not" | imbalance, "lack of balance" | ig-, il-, im-, in-, or ir- |
| in- | "not" | inactive, "not active" | ig-, il-, im-, in-, or ir- |
| infra- | "below" | infrared, "below red on the spectrum" | |
| inter- | "between" | interobserver, "between observers" | |
| intra- | "within" | intracellular, "inside a cell" | |
| ir- | "not" | irregular, "not regular" | ig-, il-, im-, in-, or ir- |
| macro- | "large-scale" ; "exceptionally prominent" | macroeconomics, "workings of entire economies" | |
| mal- | "unpleasant", "not" | malocclusion, "bad occlusion" | |
| maxi- | "big", "as big as possible" | maxi-single, "single with extras" | |
| meso- | "middle" | mesoamerican, "middle of the Americas" | |
| meta- | "self-referential" | metadata, "data that provides information about other data" | |
| micro- | "small-scale" | micrometer, "small-measurement instrument" | |
| mid- | "middle" | midportion, "middle part" | |
| mini- | "small" | miniature, "small"; "smaller version" | |
| mis- | "bad", "wrong" | misspelling, "incorrect spelling" | |
| mono- | "one" | monotheism, "belief in one god" | See number prefixes in English |
| multi- | "many", "more than one" | multiplex, "many signals in one circuit" | |
| non- | "no", "not" | nonstop, "without stopping" | |
| octo- | "eight" | octopus, "eight-footed" | See number prefixes in English |
| over- | "excess", "too much"; "on top" | overexpression, "too much expression" overcoat, "outer coat" | |
| pan- | "all" | pancytopenia, "low counts across all cell types" pan-American, "involving all of the Americas" pansexual, "sexually attracted to people of all genders" | Sometimes "all-" is used, especially in Asian English, where All-Union was a standard translation of the Russian word meaning "pan-USSR" or "USSR-wide", and "All-India" is a similar standard term in India, comparable to words such as national, nationwide, or federal. |
| para- | "beside"; "beyond"; "related to"; "altered" | paranormal, "beyond the normal" paresthesia, "altered sensation" paramilitary, "military-like" | |
| penta- | "five" | pentateuch, "the five books of Moses" | See number prefixes in English |
| per- | "through"; "throughout" | percutaneous, "through the skin" | |
| peri- | "around" | pericardial, "around the heart" | |
| poly- | "many" | polyglot, "many languages" | |
| post- | "after" | postoperative, "after surgery" | |
| pre- | "before"; "already" | preassembled, "already built" | |
| pro- | "on behalf of" ; "before" | pro-science, "in favor of science" | |
| proto- | "first"; "primitive"; "precursor" | Proto-Indo-European, "precursor of Indo-European" prototype, "first or prime example" | |
| pseudo- | "false", "specious" | pseudonym, "fake name" | |
| quadri- | "four" | quadrilateral, "four-sided" | See number prefixes in English |
| quasi- | "somewhat", "resembling" | quasiparticulate, "resembling particles" | |
| re- | "again" | reestablish, "establish again" | |
| self- | " oneself" | self-cleaning, "cleans itself" | By normative convention, always hyphenated |
| semi- | "partial"; "somewhat"; "half" | semiarid, "somewhat arid" | See number prefixes in English |
| sub- | "below" | subzero, "below zero" | |
| super- | "above"; "more than"; "great" | supermarket, "big market" | |
| supra- | "above" | supraorbital, "above the eye sockets" | |
| tetra- | "four" | tetravalent, "four valence electrons" | See number prefixes in English |
| trans- | "across"; "connecting" | transatlantic, "across the Atlantic Ocean" | |
| tri- | "three" | tripartite, "three parts" | |
| ultra- | "beyond"; "extremely" | ultraviolet, "beyond violet on the spectrum" | |
| un- | "not"; "remove"; "opposite" | unopened, "not opened" | |
| under- | "beneath"; "not enough" | underexposure, "not enough exposure" | |
| up- | "up"; "increase" | upshift, "shift to a higher gear" upregulation, "regulation toward increased expression" | |
| xeno- | "foreign" | xenophobia, "fear of strangers or foreigners" xenotransplantation, "transplant from another species" |