English prefixes areaffixes (i.e., boundmorphemes that provide lexical meaning) that are added before either simpleroots or complexbases (oroperands) consisting of (a) a root and other affixes, (b) multiple roots, or (c) multiple roots and other affixes. Examples of these follow:

• undo (consisting of prefixun- and rootdo)
• untouchable (consisting of prefixun-, roottouch, and suffix-able)
• non-childproof (consisting of prefixnon-, rootchild, andsuffix-proof)
• non-childproofable (consisting of prefixnon-, rootchild, rootproof, and suffix-able)

English words may consist of multiple prefixes:anti-pseudo-classicism (containing both ananti- prefix and apseudo- prefix).

In English, all prefixes arederivational. This contrasts with English suffixes, which may be either derivational orinflectional.

As is often the case with derivational morphology, many English prefixes can only be added to bases of particularlexical categories (or "parts of speech"). For example, the prefixre- meaning "again, back" is only added to verb bases as inrebuild,reclaim,reuse,resell,re-evaluate,resettle. It cannot be added to bases of other lexical categories. Thus, examples ofre- plus a noun base (such as the ungrammatical*rehusband,*remonopoly) orre- plus an adjective base (*renatural,*rewise) are virtually unattested.^[1]

These selectional restrictions on what base a prefix can be attached to can be used to distinguish between otherwise identical-sounding prefixes. For instance, there are two differentun- prefixes in English: one meaning "not, opposite of", the other meaning "reverse action, deprive of, release from". The first prefixun- "not" is attached to adjective and participle bases while the second prefixun- "reverse action" is attached to either verb or noun bases. Thus, English can have two words that are pronounced and spelled the same and have the same lexical category but have different meanings, different prefixes, a different internal morphological structure, and different internal bases that the prefixes are attached to:

• unlockable "not able to be locked"
• unlockable "able to be unlocked"

In the firstunlockable "not able to be locked", the prefixun- "not" is attached to an adjective baselockable (which, in turn, is composed oflock +-able). This word has the following internal structure:

[ un [ [ lock ]_verb able ]_adj ]_adj

In the secondunlockable "able to be unlocked", the prefixun- "reverse action" is attached to a verb baselock, resulting in the derived verbunlock. Subsequently, the-able suffix is added after the newly createdunlock verb base deriving the adjectiveunlockable. This word has the following internal structure:

[ [ un [ lock ]_verb ]_verb able ]_adj

Only certain verbs or nouns can be used to form a new verb having the opposite meaning. In particular, using verbs describing an irreversible action produces words often considered nonsense, e.g.unkill, unspend, unlose, unring. These words may nevertheless be in occasional use for humorous or other effect.

Unlike derivational suffixes, English derivational prefixes typically do not change the lexical category of the base (and are so calledclass-maintaining prefixes). Thus, the worddo, consisting of a single morpheme, is a verb, as is the wordredo, which consists of the prefixre- and the base rootdo.

However, there are a few prefixes in English that areclass-changing in that the word resulting after prefixation belongs to a lexical category that is different from the lexical category of the base. Examples of this type includea-,be-, anden-.a- typically creates adjectives from noun and verb bases:blaze (noun/verb) >ablaze (adj). The relativelyunproductivebe- creates transitive verbs from noun bases:witch (noun) >bewitch (verb).en- creates transitive verbs from noun bases:slave (noun) >enslave (verb).

Several English words are analyzed as a combination of a dependent affix and an independent base, such as those found in words likeboy-hood orun-just. Following Marchand (1969), these types of words are formed bynative word-formation processes.

Other words in English (and also in French and German) are formed viaforeign word-formation processes, particularly processes seen in Greek and Latin word-formation. These word types are often known asneo-classical (orneo-Latin) words and are often found in academic learned vocabulary domains (such as in science fields), as well as ininkhorn terms coined in the 17th and 18th centuries. Words of this nature are borrowed from either Greek or Latin or have been newly coined based upon Greek and Latin word-formation processes. It is possible to detect varying degrees of foreignness.^[2]

In some analytic frameworks, such neo-classical prefixes are excluded from analyses of English derivation on the grounds that they are not analyzable according to a mostly synchronic (that is, relatively productive or easily recognizable and relating to present-day idioms) English (that is, "native") basis.^[3] Conceptualized thus, anglicized neo-classical English words such asdeceive are not analyzed by Marchand as being composed of a prefixde- and a bound base-ceive but are rather analyzed as being composed of a single morpheme (although the Latin sources of these English words are analyzed as such, as "native" Latin components in the Latin language).^[4] Similarly, pairs such asdefend/defense anddouble (or duple)/duplicity are not considered morphologically related in Marchand's treatment of English word formation and are thus excluded too, though they are regarded as derivatives of the shared roots in Jespersen's and Koizul's, while in others, they may be seen asallomorphs or variants (likedeep/depth, a pair formed of Germanic components). However, not all foreign words are unanalyzable according to such an English basis: some foreign elements have been nativized and have become a part of productive English word-formation processes. An example of such a now native English prefix isco- as inco-worker, which is ultimately derived from the Latin prefixcom- (with its allomorphsco-,col-,con-, andcor-); andex- as inex-soldier, which derives from the Latinex-.

• Combining form

• Number prefix
• English grammar
• English compound
• Affix
• List of Greek and Latin roots in English

• Adams, Valerie. (1973).An introduction to modern English word-formation. London: Longman.
• Ayers, Donald M. (1986).English words from Latin and Greek elements (2nd & rev. ed.). Tucson: The University of Arizona Press.
• Bauer, Laurie. (1983).English word-formation. Cambridge: Cambridge University Press.
• Bauer, Laurie; Lieber, Rochelle; Plag, Ingo (2013).The Oxford Reference Guide to English Morphology. Oxford, UK: Oxford University Press.
• Brown, Roland W. (1927).Materials for word-study: A manual of roots, prefixes, suffixes and derivatives in the English language. New Haven, CT: Van Dyck & Co.
• Cannon, Garland Hampton. (1987).Historical change and English word-formation: Recent vocabulary. New York: P. Lang.
• Jespersen, Otto. (1942).A modern English grammar on historical principles: Morphology (Part 6). London: George Allen & Unwin and Ejnar Munksgaard.
• Marchand, Hans. (1969).The categories and types of present-day English word-formation (2nd ed.). München: C. H. Beck.
• Quirk, Randolph; Greenbaum, Sidney; Leech, Geoffrey; & Svartvik, Jan. (1985). Appendix I: Word-formation. InA comprehensive grammar of the English language (pp. 1517–1585). Harlow: Longman.
• Simpson, John (Ed.). (1989).Oxford English dictionary (2nd ed.). Oxford: Oxford University Press.

• Chart of English Language Roots

• English grammar
• Prefixes

• Articles with short description
• Short description is different from Wikidata