declension

n. (Grammar) variation of the form (of a noun, verb, etc.); decline, descent, slope

In linguistics, declension (or declination) is the inflection of nouns, pronouns and adjectives to indicate such features as number (typically singular vs. plural), case (subject, object, and so on), or gender. Declension occurs in a great many of the world's languages, and features very prominently in many Indo-European languages, but is much less prominent in English; English nouns only decline to distinguish singular from plural (e.g. book vs. books), English adjectives do not decline at all, and only a few English pronouns show vestiges of case-triggered declension (e.g. subjective he vs. objective him).
See more at Wikipedia.org...

Noun
1. the inflection of nouns and pronouns and adjectives in Indo-European languages
(hypernym) inflection, inflexion
(member-meronym) noun
(derivation) decline
2. process of changing to an inferior state
(synonym) deterioration, decline in quality, worsening
(hypernym) decline, diminution
(hyponym) slump, slack, drop-off, falloff, falling off
(derivation) worsen, decline
3. a downward slope or bend
(synonym) descent, declivity, fall, decline, declination, downslope
(hypernym) slope, incline, side
(hyponym) downhill
(derivation) decline
4. 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"
(hypernym) class, category, family
(derivation) decline

(n.)
The form of the inflection of a word declined by cases; as, the first or the second declension of nouns, adjectives, etc.
  

(n.)
The act or the state of declining; declination; descent; slope.
  

(n.)
Rehearsing a word as declined.
  

(n.)
Inflection of nouns, adjectives, etc., according to the grammatical cases.
  

(n.)
Act of courteously refusing; act of declining; a declinature; refusal; as, the declension of a nomination.
  

(n.)
A falling off towards a worse state; a downward tendency; deterioration; decay; as, the declension of virtue, of science, of a state, etc.
  

Synonyms and related words:
IC analysis, abnegation, accidence, affix, affixation, allomorph, bound morpheme, cascade, catabasis, cataract, chute, collapse, comedown, conjugation, contradiction, crash, cutting, debacle, debasement, decadence, decadency, deceleration, declination, declinature, decline, decline and fall, declining, decrescendo, defluxion, deformation, degeneracy, degenerateness, degeneration, degradation, demotion, denial, depravation, depravedness, depreciation, deprivation, derivation, derogation, descending, descension, descent, deterioration, devolution, difference of form, dilapidation, diminuendo, disagreement, disallowance, disclaimer, disclamation, disobedience, dissent, dive, down, downbend, downcome, downcurve, downfall, downflow, downgrade, downpour, downrush, downtrend, downturn, downward mobility, downward trend, drop, dropping, dwindling, dying, ebb, effeteness, enclitic, fading, failing, fall, falling, falling-off, formative, free form, gravitation, holding back, immediate constituent analysis, inclination, infix, infixation, inflection, involution, lapse, loss of tone, morph, morpheme, morphemic analysis, morphemics, morphology, morphophonemics, nay, negation, negative, negative answer, nix, no, nonacceptance, noncompliance, nonconsent, nonobservance, paradigm, plummeting, plunge, pounce, prefix, prefixation, proclitic, radical, rapids, recantation, refusal, regression, rejection, remission, repudiation, retention, retreat, retrocession, retrogradation, retrogression, root, ruination, slippage, slowdown, slump, stem, stoop, subsidence, suffix, suffixation, swoop, theme, thumbs-down, turndown, unwillingness, wane, waterfall, withholding, word-formation