Aplanatic focusof a lens (Opt.), the point or focus from which rays diverging pass the lens without spherical aberration. In certain forms of lenses there are two such foci; and it is by taking advantage of this fact that the best aplanatic object glasses of microscopes are constructed.

(A*plan"a*tism) n. Freedom from spherical aberration.

(A*plas"tic) a. [Pref. a- not + plastic.] Not plastic or easily molded.

(||A`plomb") n. [F., lit. perpendicularity; to + plomb lead. See Plumb.] Assurance of manner or of action; self-possession.

(A*plot"o*my) n. [Gr. simple + a cutting.] (Surg.) Simple incision. Dunglison.

(||A*plus"tre) n. [L., fr. Gr. .] (Rom. Antiq.) An ornamental appendage of wood at the ship's stern, usually spreading like a fan and curved like a bird's feather. Audsley.

(||A*plys"i*a) n. [Gr. a dirty sponge, fr. unwashed; 'a priv. + to wash.] (Zoöl.) A genus of marine mollusks of the order Tectibranchiata; the sea hare. Some of the species when disturbed throw out a deep purple liquor, which colors the water to some distance. See Illust. in Appendix.

(||Ap*neu"mo*na) n. pl. [NL., fr. Gr. 'a priv. + a lung.] (Zoöl.) An order of holothurians in which the internal respiratory organs are wanting; — called also Apoda or Apodes.

(||Ap*nœ"a) n. [NL., fr. Gr. 'a priv. + breath, to breathe, blow.] (Med.) Partial privation or suspension of breath; suffocation.

(Ap"o) Ab-.]—> A prefix from a Greek preposition. It usually signifies from, away from, off, or asunder, separate; as, in apocope (a cutting off), apostate, apostle (one sent away), apocarpous.

(A*poc"a*lypse) n. [L. apocalypsis, Gr. fr. to uncover, to disclose; from + to cover, conceal: cf. F. apocalypse.]

1. The revelation delivered to St. John, in the isle of Patmos, near the close of the first century, forming the last book of the New Testament.

Apish to Apophasis

(Ap"ish) a. Having the qualities of an ape; prone to imitate in a servile manner. Hence: Apelike; fantastically silly; foppish; affected; trifling.

The apish gallantry of a fantastic boy.
Sir W. Scott.

(Ap"ish*ly), adv. In an apish manner; with servile imitation; foppishly.

(Ap"ish*ness), n. The quality of being apish; mimicry; foppery.

(A*pit"pat), adv. [Pref. a- + pitpat.] With quick beating or palpitation; pitapat. Congreve.

(Ap`la*cen"tal), a. [Pref. a- + placental.] Belonging to the Aplacentata; without placenta.

(||Ap`la*cen*ta"ta), n. pl. [Pref. a- not + placenta.] (Zoöl.) Mammals which have no placenta.

(||Ap`la*coph"o*ra) n. pl. [NL., fr. Gr. 'a priv. + a flat cake + to bear.] (Zoöl.) A division of Amphineura in which the body is naked or covered with slender spines or setæ, but is without shelly plates.

(Ap`la*nat"ic) a. [Gr. 'a priv. + disposed to wander, wandering, to wander.] (Opt.) Having two or more parts of different curvatures, so combined as to remove spherical aberration; — said of a lens.

  By PanEris using Melati.

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