The only necessary part of speech in a predicate is a verb, but a complete predicate may include any other part of speech, with the possible exception of an interjection.
I believe it is a subject complement, what used to be called a predicative adjective. Game over is really a kind of contraction of The game is over.
Expression is a noun.
"Concise" is an adjective. It describes something that is expressed in a clear and brief manner.
This tasty eggplant dish is a favorite in Greece.
"to water the earth" is a verbal phrase- more precisely an infinitive phrase. It could be expressed as "to irrigate"
Predicative possessive pronouns are those who are used without the noun and instead of the noun to which they refer : Whose coat is this ? It is mine (my coat).
A predicate noun (more correctly called a predicative noun) is a type of complement. The complement element of a clause adds meaning to that of another clause element - either the subject (the subject complement), or the object (the object complement). A subject complement (Cs) renames the subject, for example in 'John is an accountant', 'John' is the subject and 'an accountant' is a subject complement (predicative noun). An object complement (Co) renames the object, for example in 'I find your children angels', 'children' is the object and 'angels' is an object complement (predicative noun). Be careful to avoid confusing 'predicative nouns' with 'predicative adjectives' - the latter describes rather than renames the subject or object. In the above examples if you replace 'an accountant' and 'angels' with 'fat' and 'charming' respectively, these would be predicative adjectives.
The word "vehement" is an adjective. It is used to describe strong emotions or feelings expressed in a forceful way.
The attributive use of adjectives comes before the noun it describes, while the predicative use comes after a linking verb and describes the subject.
The part of speech for this particular word is a noun.
part of speech
The part of speech for "answer" is a noun.