Etymology: < classical Latin ex-, combining form of ex (preposition) out of (see ex prep.). In Latin the form ex- appears before vowels and h ; also before c , p (except in ēpotāre , ēpōtus ), q , s , t ; before f it becomes ef- (in inscriptions ec- : compare ancient Greek ἐκ ); before other consonants (except in exlex ) it becomes ē . All these various forms are represented in many English derivatives; e.g. ebullient adj., effervesce v., extend v. An s following the prefix was in medieval spelling commonly omitted, and this practice has been adopted in English orthography, as in exert v., extinct adj.; in some scientific terms, however, the s has been retained in order to exhibit the composition more clearly, as in exsert v. to protrude (etymologically equivalent to exert v.), exsanguineous adj., exsiccate adj. The euphonic rules affecting the prefix in classical Latin did not prevail in post-classical Latin, the universal form being ex- , represented in Romance languages by es- (see es- prefix). In Old French and in Middle English, words with the prefix es- were occasionally written with ex- , after the analogy of words adopted from Latin; a few of these remodelled forms remain in modern English, as exchange v., expound v. The Latin compounds of ex- chiefly belong to the following classes, all which are represented by English derivatives. 1. Verbs formed from other verbs; in some of these ex- has its primary force of ‘out’, ‘forth’, as in exclūdere exclude v., exīre (see exit n.); in some it means ‘upward’, as in extollere extol v.; in others it has the sense ‘thoroughly’, as in excruciāre excruciate v. 2. Verbs formed from adjectives, with general sense ‘to bring into a certain state’, as exacerbāre exacerbate v., exasperāre exasperate v. 3. Verbs formed from nouns; some of these are really formed on phrases in which ex governs the noun, and have the senses to ‘to remove, expel, or relieve from (that which is denoted by the noun)’, as excūsāre excuse v., expatriāre expatriate v., exonerāre exonerate v.; others have the sense ‘to deprive of (what is denoted by the noun)’, as excoriāre excoriate v., excorticāre excorticate v. 4. Adjectives formed from nouns, with the general sense ‘deprived of something’, as exsanguis bloodless (see exsanguineous adj.); in imitation of these, many terms of modern science have been formed in which ex- has the non-Latin sense ‘destitute of’, as exalbuminous adj., exstipulate adj.; the form e- (see e- prefix²) has however been employed more frequently, even where Latin euphony would require ex- , as in ecaudate adj.In post-classical Latin the prefix ex- is used before nouns or adjectives to denote a role that a person no longer exercises, e.g. exconsul (5th cent., from the phrase ex consule (5th cent.); compare quot. a1398 at sense 2a(a)), exconsularis exconsular (5th cent.; compare quot. 1683 at sense 2a(a)). Compare the patttern of derivation seen in e.g. classical Latin prōcōnsul proconsul n.¹, prōpraetor propraetor n. from the earlier prō cōnsule , prō praetōre . In later post-classical Latin this usage was greatly extended, as seen in such forms as ex-Augustus ex-emperor (12th cent.). Some words of this formation (e.g. ex-professor (1627 or earlier)) passed in adapted forms into Italian and French (compare French exprofesseur (1641 or earlier)), and on the analogy of these ex- was prefixed to other words in Romance languages. The English use, imitated from French, seems to have first become common towards the end of the 18th cent. (compare e.g. quots. 1793 at sense 2a(a), 1796 at sense 2a(a)) When it has primary or secondary stress, the prefix is pronounced Brit. /ɛks/, U.S. /ɛks/ or Brit. /ɪks/, U.S. /ɪks/; in unstressed position this remains before a (written) consonant; before a stressed vowel the pronunciation is usually Brit. /ɛɡz/, U.S. /ɛɡz/ or Brit. /ɪɡz/, U.S. /ɪɡz/; this rule, however, has many exceptions, chiefly in rare words and in words affected by the analogy of cognates differently accented. In the more common of the words beginning exh- , such as exhaust v., exhibit v., the h is usually silent in English; many people, however, sound it (especially in deliberate or public utterance) when the word has the stress on the second syllable. To avoid inconvenient repetition the more frequent of the two alternative pronunciations will alone be indicated in this dictionary. In words of little colloquial currency the h is ordinarily sounded when it begins a stressed syllable.

Etymology: < (i) post-classical Latin ex- and its etymon (ii) ancient Greek ἐξ- out, away, off, use as prefix of ἐξ (preposition) out of < the same Indo-European base as classical Latin ex (see ex prep. and compare ex- prefix¹), occurring only before vowels.Compare French ex- . Before consonants it is replaced in Greek by the related and synonymous form ἐκ- , Latin ec- , as reflected in English by ecbasis n., eccentric adj., eclipse n., ecstasy n., etc.