the inflection of nouns, pronouns, and adjectives for categories such as case and number.
b.
the whole set of inflected forms of such a word, or the recital thereof in a fixed order.
c.
a class of such words having similar sets of inflected forms: the Latin second declension.
2.
an act or instance of declining.
3.
a bending, sloping, or moving downward: land with a gentle declension toward the sea.
4.
deterioration; decline.
5.
deviation, as from a standard.
[Origin: 1400–50; late ME declenson, declynson (with suffix later assimilated to -sion), by stress retraction and syncope < OF declinaison < L déclīnātiōdeclination]
a class of nouns or pronouns or adjectives in Indo-European languages having the same (or very similar) inflectional forms; "the first declension in Latin"
De*clen"sion\, n. [Apparently corrupted fr. F. d['e]clinaison, fr. L. declinatio, fr. declinare. See Decline, and cf. Declination.]1. The act or the state of declining; declination; descent; slope. The declension of the land from that place to the sea. --T. Burnet. 2. A falling off towards a worse state; a downward tendency; deterioration; decay; as, the declension of virtue, of science, of a state, etc. Seduced the pitch and height of all his thoughts To base declension. --Shak. 3. Act of courteously refusing; act of declining; a declinature; refusal; as, the declension of a nomination. 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. Note: 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. Declension of the needle, declination of the needle.