Finnish Language Question?
What is the difference between Soulainen and Soulaista?
As suolainen (prativiivi: suolaista) is an adjective, it can be used as attribute to a noun (i.e. beside the noun). Then there both noun and adjective take the same case. When the adjective stands after "on" it must sometimes take partitiivi, because of the content of the noun (cf. link in the other comment).