Part 400

Syn. -- Invasion; incursion; inroad. See Invasion.

Ir*rup"tive (?), a. Rushing in or upon.

Ir"ving*ite (?), n. (Eccl.) The common designation of one a sect founded by the Rev. Edward Irving (about 1830), who call themselves the Catholic Apostolic Church. They are highly ritualistic in worship, have an elaborate hierarchy of apostles, prophets, etc., and look for the speedy coming of Christ.

Is- (?). See Iso-.

Is (?), v. i. [AS. is; akin to G. & Goth. ist, L. est, Gr. &?;, Skr. asti. √9. Cf. Am, Entity, Essence, Absent.] The third person singular of the substantive verb be, in the indicative mood, present tense; as, he is; he is a man. See Be.

In some varieties of the Northern dialect of Old English, is was used for all persons of the singular.

For thy is I come, and eke Alain.

Chaucer.

Aye is thou merry.

Chaucer.

The idiom of using the present for future events sure to happen is a relic of Old English in which the present and future had the same form; as, this year Christmas is on Friday.

To-morrow is the new moon.

1 Sam. xx. 5.

{ Is"a*bel (?), n., Is"a*bel col"or (?). } [F. isabelle.] See Isabella.

{ Is`a*bel"la (?), n., Is`a*bel"la col"or (?) }. [Said to be named from the Spanish princess Isabella, daughter of king Philip II., in allusion to the color assumed by her shift, which she wore without change from 1601 to 1604, in consequence of a vow made by her.] A brownish yellow color.

Is`a*bel"la grape` (?). (Bot.) A favorite sweet American grape of a purple color. See Fox grape, under Fox.

Is`a*bel"la moth` (?; 115). (Zoöl.) A common American moth (Pyrrharctia isabella), of an isabella color. The larva, called woolly bear and hedgehog caterpillar, is densely covered with hairs, which are black at each end of the body, and red in the middle part.

Is`a*bel"line (?), a. Of an isabel or isabella color.

Is*ag"e*lous (s*g"*ls), a. [Is- + Gr. a`gelos information.] Containing the same information; as, isagelous sentences. "The coded message and the original, though appearing entirely unlike, are completely isagelous." Bacon "The complementary strands have isagelous sequences." J. D. Watson. -- Is"a*gel n. One of two or more objects containing the same information.

I"sa*goge (?), n. [L., fr. Fr. &?;, fr. &?; to introduce; &?; into + &?; to lead.] An introduction. [Obs.] Harris.

{ I"sa*gog"ic (?), I"sa*gog"ic*al (?), } a. [L. isagogicus, Gr. &?;.] Introductory; especially, introductory to the study of theology.

I"sa*gog"ics (?), n. (Theol.) That part of theological science directly preliminary to actual exegesis, or interpretation of the Scriptures.

I"sa*gon ("s*gn), n. [Gr. 'i`sos equal + gwni`a angle: cf. F. isagone, a.] (Math.) A figure or polygon whose angles are equal.

Is*ap`os*tol"ic (?), a. [Gr. &?;.] Having equal, or almost equal, authority with the apostles of their teachings.

{ I*sat"ic (?), I`sa*tin"ic (?), } a. (Chem.) Pertaining to, or derived from, isatin; as, isatic acid, which is also called trioxindol.

I"sa*tide (?), n. (Chem.) A white crystalline substance obtained by the partial reduction of isatin. [Written also isatyde.]

I"sa*tin (?), n. [See Isatis.] (Chem.) An orange-red crystalline substance, C8H5NO2, obtained by the oxidation of indigo blue. It is also produced from certain derivatives of benzoic acid, and is one important source of artificial indigo. [Written also, less properly, isatine.]

||I"sa*tis (?; 277), n. [L., a kind of plant, Gr. &?; woad.] (Bot.) A ||genus of herbs, some species of which, especially the Isatis ||tinctoria, yield a blue dye similar to indigo; woad. || I*sat"o*gen (?), n. [Isatin + -gen.] (Chem.) A complex nitrogenous radical, C8H4NO2, regarded as the essential residue of a series of compounds, related to isatin, which easily pass by reduction to indigo blue. -- I*sat`o*gen"ic (#), a.