[de.clen.sion] n [ME declenson, modif. of MF declinaison, fr. L declination-, declinatio grammatical inflection, turning aside, fr. declinare to inflect, turn aside] (15c) 1 a: noun, adjective, or pronoun inflection esp. in some prescribed order of the forms b: a class of nouns or adjectives having the same type of inflectional forms
2: a falling off or away: deterioration
3: descent, slope -- de.clen.sion.al adj