In certain languages, the inflection of nouns, pronouns, and adjectives in categories such as case, number, and gender.
A class of words of one language with the same or a similar system of inflections, such as the first declension in Latin.
A descending slope; a descent.
A decline or decrease; deterioration: "States and empires have their periods of declension"(Laurence Sterne).
A deviation, as from a standard or practice.
[Middle English declenson, from Old French declinaison, from Latin dēclīnātiō, dēclīnātiōn-, grammatical declension, declination; see declination.] de·clen'sion·al adj.
[di-klen-shuh-nl] 
ʃə