n. [ Apparently corrupted fr. F. déclinaison, fr. L. declinatio, fr. declinare. See Decline, and cf. Declination. ] 1. The act or the state of declining; declination; descent; slope. [ 1913 Webster ]

The declension of the land from that place to the sea. T. Burnet. [ 1913 Webster ]

2. A falling off towards a worse state; a downward tendency; deterioration; decay; as, the declension of virtue, of science, of a state, etc. [ 1913 Webster ]

Seduced the pitch and height of all his thoughts
To base declension. Shak. [ 1913 Webster ]

3. Act of courteously refusing; act of declining; a declinature; refusal; as, the declension of a nomination. [ 1913 Webster ]

4. (Gram.) (a) Inflection of nouns, adjectives, etc., according to the grammatical cases. (b) The form of the inflection of a word declined by cases; as, the first or the second declension of nouns, adjectives, etc. (c) Rehearsing a word as declined. [ 1913 Webster ]

☞ The nominative was held to be the primary and original form, and was likened to a perpendicular line; the variations, or oblique cases, were regarded as fallings (hence called casus, cases, or fallings) from the nominative or perpendicular; and an enumerating of the various forms, being a sort of progressive descent from the noun's upright form, was called a declension. Harris. [ 1913 Webster ]

Declension of the needle, declination of the needle. [ 1913 Webster ]

a. Belonging to declension. [ 1913 Webster ]

Declensional and syntactical forms. M. Arnold. [ 1913 Webster ]

v. t. [ Cf. Dan. flense, D. vlensen, vlenzen, Scot. flinch. ] To strip the blubber or skin from, as from a whale, seal, etc. [ 1913 Webster ]

the flensed carcass of a fur seal. U. S. Census (1880). [ 1913 Webster ]

[ See Fresnel lamp. ] (Optics) See under Lens. [ 1913 Webster ]

n.; pl. Lenses [ L. lens a lentil. So named from the resemblance in shape of a double convex lens to the seed of a lentil. Cf. Lentil. ] (Opt.) A piece of glass, or other transparent substance, ground with two opposite regular surfaces, either both curved, or one curved and the other plane, and commonly used, either singly or combined, in optical instruments, for changing the direction of rays of light, and thus magnifying objects, or otherwise modifying vision. In practice, the curved surfaces are usually spherical, though rarely cylindrical, or of some other figure. [ 1913 Webster ]

☞ Of spherical lenses, there are six varieties, as shown in section in the figures herewith given: viz., a plano-concave; b double-concave; c plano-convex; d double-convex; e converging concavo-convex, or converging meniscus; f diverging concavo-convex, or diverging meniscus. [ 1913 Webster ]

Crossed lens (Opt.), a double-convex lens with one radius equal to six times the other. --
Crystalline lens. (Anat.) See Eye. --
Fresnel lens (Opt.), a compound lens formed by placing around a central convex lens rings of glass so curved as to have the same focus; used, especially in lighthouses, for concentrating light in a particular direction; -- so called from the inventor. --
Multiplying lens or
Multiplying glass (Opt.), a lens one side of which is plane and the other convex, but made up of a number of plane faces inclined to one another, each of which presents a separate image of the object viewed through it, so that the object is, as it were, multiplied. --
Polyzonal lens. See Polyzonal. [ 1913 Webster ]

n. a camera lens designed to focus at short distances so as to achieve photographic magnifications of objects larger than with standard lenses. [ PJC ]

n. An object glass. See under Object, n. [ PJC ]

n. (Opt.) The half of a lens divided along a plane passing through its axis. [ 1913 Webster ]

n. a special compound camera lens with a long effective focal length but used in a camera with a short focal length, allowing large images to be obtained of distant objects when used in a camera in place of an ordinary lens; -- called also telephotographic lens. [ PJC ]