2. Disposition of the mind; propensity; as, the aptness of men to follow example. 3. Quickness of apprehension; readiness in learning; d?cility; as, an aptness to learn is more observable in some children than in others. 4. Proneness; tendency; as, the aptness of iron to rust. Ap¶tote (?), n. [L. aptotum, Gr. ? indeclinable; ? priv. + ? fallen, declined, ? to fall.] (Gram.) A noun which has no distinction of cases; an indeclinable noun. ApÏtot¶ic (?), a. Pertaining to, or characterized by, aptotes; uninflected; as, aptotic languages. Ø Ap¶tyÏchus (?), n. [NL., fr. Gr. ? priv. + ?, ?, fold.] (Zo”l.) A shelly plate found in the terminal chambers of ammonite shells. Some authors consider them to be jaws; others, opercula. Ø A¶pus (?), n. [NL., fr. Gr. ?. See Apode, n.] (Zo”l.) A genus of freshÐwater phyllopod crustaceans. See Phyllopod. Ap·yÏret¶ic (?), a. [Pref. a? not + pyretic.] (Med.) Without fever; Ð applied to days when there is an intermission of fever. Dunglison. Ø Ap·yÏrex¶iÏa (?), Ap·yÏrex·y (?), } n. [NL. apyrexia, fr. Gr. ?; ? priv. + ? to be feverish, fr. ? fire: cf. F. apyrexie.] (Med.) The absence of intermission of fever. Ap·yÏrex¶iÏal (?), a. (Med.) Relating to apyrexy. ½Apyrexial period.¸ Brande & C. Ap¶yÏrous (?), a. [Gr. ?; ? priv. + ? fire.] Incombustible; capable of sustaining a strong heat without alteration of form or properties. Ø A¶qua (?), n. [L. See Ewer.] Water; Ð a word much used in pharmacy and the old chemistry, in various signification, determined by the word or words annexed. ÷ ammoni‘, the aqueous solution of ammonia; liquid ammonia; often called aqua ammonia. Ð ÷ marine (?), or ÷ marina (?). Same as Aquamarine. Ð ÷ regia (?). [L., royal water] (Chem.), a very corrosive fuming yellow liquid consisting of nitric and hydrochloric acids. It has the power of dissolving gold, the ½royal¸ metal. Ð ÷ Tofana (?), a fluid containing arsenic, and used for secret poisoning, made by an Italian woman named Tofana, in the middle of the 17th century, who is said to have poisoned more than 600 persons. Francis. Ð ÷ vit‘ (?) [L., water of life. Cf. Eau de vie, Usquebaugh], a name given to brandy and some other ardent spirits. Shak. Ø A·qua for¶tis (?). [L., strong water.] (Chem.) Nitric acid. [Archaic] A·quaÏmaÏrine¶ (?), n. (Min.) A transparent, pale green variety of beryl, used as a gem. See Beryl. A·quaÏpunc¶ture (?), n. [L. aqua water, + punctura puncture, pungere, punctum, to, prick.] (Med.) The introduction of water subcutaneously for the relief of pain. Ø Aq·uaÏrelle¶ (?), n. [F., fr. Ital acquerello, fr. acqua water, L. aqua.] A design or painting in thin transparent water colors; also, the mode of painting in such colors. Aq·uaÏrel¶list (?), n. A painter in thin transparent water colors. AÏqua¶riÏal (?), AÏqua¶riÏan (?), } a. Of or performance to an aquarium. AÏqua¶riÏan, n. [L. (assumed) Aquarianus, fr. aqua: cf. F. Aquarien. See Aqua.] (Eccl. Hist.) One of a sect of Christian in the primitive church who used water instead of wine in the Lord's Supper. AÏqua¶riÏum (?), n.; pl. E. Aquariums (?), L. Aquaria (?). [L. See Aquarius, Ewer.] An artificial pond, or a globe or tank (usually with glass sides), in which living specimens of aquatic animals or plants are kept. Ø AÏqua¶riÏus (?), n. [L. aquarius, adj., relating to water, and n., a waterÐcarrier, fr. aqua. See Aqua.] (Astron.) (a) The WaterÐbearer; the eleventh sign in the zodiac, which the sun enters about the 20th of January; Ð so called from the rains which prevail at that season in Italy and the East. (b) A constellation south of Pegasus. AÏquat¶ic (?), a. [L. aquaticus: cf. F. aquatique. See Aqua.] Pertaining to water growing in water; living in, swimming in, or frequenting the margins of waters; as, aquatic plants and fowls. AÏquat·ic, n. 1. An ~ animal plant. 2. pl. Sports or exercises practiced in or on the water. AÏquat¶icÏal (?), a. Aquatic. [R.] Aq¶uaÏtile (?), a. [L. aquatilis: cf. F. aquatile.] Inhabiting the water. [R.] Sir T. Browne. A¶quaÏtint (?), A·quaÏtin¶ta (?), } n. [It. acquatinta dyed water; acqua (L. aqua) water + tinto, fem. tinta, dyed. See Tint.] A kind of etching in which spaces are bitten by the use of aqua fortis, by which an effect is produced resembling a drawing in water colors or India ink; also, the engraving produced by this method. Aq¶ueÏduct (?), n. [F. aqueduc, OF. aqueduct (Cotgr.), fr. L. aquaeductus; aquae, gen. of aqua water + ductus a leading, ducere to lead. See Aqua, Duke.] 1. A conductor, conduit, or artificial channel for conveying water, especially one for supplying large cities with water. µ The term is also applied to a structure (similar to the ancient aqueducts), for conveying a canal over a river or hollow; more properly called an aqueduct bridge. 2.