substitutable

Capable of being used as a substitute; valid as a replacement or alternate item.

“Stevia is not substitutable for sugar in baking: the recipes won't work; they taste terrible.”

Capable of being substituted.

(of words) interchangeable in a given context without changing the import of the expression

Capable of being exchanged for another or for something else that is equivalent

Something that can be substituted for something else; a viable replacement.