Present, Future こい is [x] こくない is not [x] Past こかった was [x] こくなかった was not [x] Te-form, Continuative こくて is [x] and... こくなくて is not [x] and... Provisional こければ if it is [x] こくなければ if it is not [x] Conditional こかったら when/if it is [x] こくなかったら when/if it is not [x] Adverbial こく [x]-ly Noun form こさ [x]-ness