The word semantics basically refers to the concept of meaning in relation to language. We can conceptualize 'meaning' in many ways, recognize language in many guises, and consider many aspects of relationship. Hence 'semantics' has many referents.
This article focuses on human natural language and meaning qualifying as 'linguistic meaning'. We therefore begin with an explication of 'natural language' and of 'linguistic meaning'.
Rule to Rule Hypothesis
An important idea in the semantics of natural languages is the rule to rule hypothesis. The idea is that any phrase structure rule or, more generally, syntactic construct, will have a corresponding semantic relationship. Thus, in the sentence
John sees Sally.
the relationship between John and Sally established by the verb see must correspond to a relationship on the level of models to which the verb see is mapped.