What are definite languages? How do you formally define them?
A language L is definite if there is some k(> 0) such that for any string w, whether w ∈ L depends on the last k symbols of w.


There is of course room for interpretation here. Assuming they mean "[it] only depends on the last $k$ symbols of $w$", here's a slightly more precise rephrasing:


  A language L is definite if there is some $k$ so that all words that share the same $k$-suffix are either in or not in the language.


Try to work from here.