Declinable
/dɪˈklaɪnəbəɫ/
"Declinable" in a Sentence (2 examples)
The word пальто (coat) isn't declinable.
It is obvious that the system in present-day English is radically different, and that the notion of case (i.e. a form or modification of a declinable word) is now of very little significance.