Subject, Predicate, Predicator

 - tells us who performs the action denoted by the verb
 - tells us who or what the sentence is about

 - to specify what the subject is engaged in doing
 - stative / dynamic

nonreferential it / existential there : meaningless

Subject (distributional tests) - by referring to syntactic positions and environments in sentences
1. predominantly consist of groups of words whose most important element denotes a person, an animal, a group of people, an institution, or a thing (NPs)
2. the first NP
3. obligatory
4. Subject-verb agreement
5. Yes/No question, position changes
6. Tag question, referred back 

Sentence : Subject + Predicate
V + NP + ...

 - specify the bare-bone content of the sentences in which they occur (the main action or process denoted by the Verb)