The key structures (which you must know for the IB are):
A noun is a word that functions as the name of some specific thing or set of things, such as living creatures, objects, places, actions, qualities, states of existence, or ideas. Linguistically, a noun is a member of a large, open part of speech whose members can occur as the main word in the subject of a clause, the object of a verb, or the object of a preposition. 
A verb is a word (part of speech) that in syntax conveys an action (bring, read, walk, run, learn), an occurrence (happen, become), or a state of being (be, exist, stand). 
In linguistics, syntax is the set of rules, principles, and processes that govern the structure of sentences (sentence structure) in a given language, usually including word order. 
Semantics is the linguistic and philosophical study of meaning, in language, programming languages, formal logics, and semiotics. It is concerned with the relationship between signifiers—like words, phrases, signs, and symbols—and what they stand for in reality, their denotation.
- Identify the key structures of natural language.