"My neighbor is Slovak."

Translation: Můj soused je Slovák.

[Phillip_Beck]

In almost all of these exercises, the word 'Slovak' is used incorrectly. It is a noun, and should only be used to refer to a person from Slovakia. 'My neighbour is Slovak' is using the noun as an adjective, and should have the indefinite article 'a' before it. The correct adjective form is 'Slovakian'.

[endless_sleeper]

Please check a respectable dictionary. You will find that Slovak and Slovakian are synonyms.