| 释义 |
▪ I. di-, prefix1|dɪ, daɪ|
repr. L. dī-, reduced form of dis-, used in L. before the consonants b, d, g (usually), l, m, n, r, s + cons., v, and sometimes before j, as in dī-būcināre, dī-dūcĕre, dī-gestio, dī-gressio, dī-jūdicāre, dī-jungĕre and dis-jungĕre, dī-lātāre, dī-minuĕre, dī-missio, dī-numerāre, dī-rectus, dī-ruptio, dī-spersus, dī-stinguĕre, dī-strictus, dī-vertĕre. Often changed back in late L. and Romanic popular words to the full form dis-, whence dismiss, disrupt; but in mod. Eng. generally di-. In OF. and ME. often varying with de-, whence defer, demission n.2, devise, from L. differre, dīmissio, dīvīsa. This took place especially before a radical beginning with s + cons., where di- was phonetically identified with dis-, and shared in the alternation of dis-:—des- (de- 6, des-, dis-). Thus in ME. desperse, destinct, destill, destrain, destress for dis-; and per contra dispair, dispise, dispite, dispoil, distroy for de-. For its force in composition, see dis-: it is not, like the latter, a living prefix. The historical pronunciation in an unstressed syllable is |dɪ-|; cf. divide, diversion, diminish; but in cases where there is a parallel word in de-, as delate, dilate, it is usually pronounced |daɪ-| for the sake of distinction, and the present tendency is to extend |daɪ-| to other words, as digest, dilute, diluvium, diradiation, direct, diverge, diverse, divest. This seems due partly to analysis of the compound, partly to the influence of stressed forms as ˈdigest n. ˈdivers, in which the i is long and diphthongal.
▪ II. di-, prefix2|daɪ, dɪ|
repr. Gr. δι- for δίς twice, as in δίγαµος twice married, δίγλωττος double-tongued, bilingual, δίδραχµος worth two drachmas, δίπτυχος double-folded. Hence:
1. Entering into numerous Eng. words, mostly technical, as dichromic, dicotyledon, digamma, digamy, diglot, digraph, dilemma, diphthong, diptych, distich, disyllable; also in the nomenclature of Natural History as Diadelphia, Diandria, Didelphia, Diptera: which see in their alphabetical places. So in Crystallography, as in di-tetrahedron a crystal having twice four sides or planes; so di-hexahedron, etc.
2. As a living prefix, used in Chemistry, with the names of compounds and derivatives, in the general sense ‘twice, double’, but with various special applications.
a. With the names of classes of compounds, as bromide, oxide, sulphide, cyanide, acetate, chlorate, nitrate, sulphate, amide, amine, etc., expressing the presence of two atoms or combining equivalents of the element or radical, as carbon dioxide CO2, manganese dichloride Mn Cl2.
⁋In the earlier part of the 19th c. the use was different: the Latin prefix bi- was then used, where di- is now, to express two proportions of the chlorous constituent, as in bi-chloride of mercury = corrosive sublimate; while the Greek di- was used to express two proportions of the basic constituent; thus calomel, when supposed to contain two of mercury to one of chlorine, was called a di-chloride.
b. With the names of specific compounds (chiefly organic), indicating a body having twice the formula of a given compound; used chiefly with the names of hypothetical radicals, to indicate the free state of these (supposed to be that of a double molecule), as in di-allyl, dibenzyl, dicyanogen.
In diphenol, the use is less exact, since this substance has not exactly the constitution of two molecules of phenol.
c. With the name (or combining form of the name) of an element or radical, expressing the presence of two atoms or molecules of that body, as in di-hydr(o)-, di-oxy-, di-carbon-, di-carb(o)-, di-nitr(o)-, di-az(o)-, di-chlor(o)-, di-brom(o)-, di-iod(o)-, di-sulph(o)-, di-phosph(o)-, di-bor(o)-, di-arsen(o)-, di-ammoni(o)-, di-amm(o)-, di-amid(o)-, di-cyan(o)-, di-methyl-, di-ethyl-, di-propyl-, di-amyl-, di-allyl-. Used especially in organic chemistry, to indicate that two atoms or molecules of the body take the place of two atoms of hydrogen, as in dibromomethane, dichlorobenzene.
d. These formations (c) are sometimes used attributively or adjectively as separate words, as di-azo compounds, di-carbon series, di-phenyl group. So with other adjectives, as diacid, dihydric, diphenic.
e. On the preceding classes of words derivatives are formed, as diazotize, diazotype, dichromated.
▪ III. di-, prefix3
the form of dia- used before a vowel, as in di-acoustic, di-æresis, di-esis, di-ocese, di-optric, di-orama. |