The Collaborative International Dictionary
Derivational
Derivational \Der`i*va"tion*al\, a.
Relating to derivation.
--Earle.
Wiktionary
derivational
a. Of or pertaining to derivation; relating to that which is derived.
WordNet
derivational
adj. characterized by inflections indicating a semantic relation between a word and its base; "the morphological relation between `sing' and `singer' and `song' is derivational" [ant: inflectional]
Usage examples of "derivational".
As discussed above, A-stems where the final -a is only part of a longer derivational ending (most often -ya or -ta) are much more common.
If derivational endings can be added to the noun hecil with no further complications, then it is perhaps also permissible to attach case endings to these nouns in -il with no strange things happening to the noun-stem itself.