Semantics is the study of meaning of a word, phrase, sentence, or text. It is a specific segment of linguistics and logic dedicated towards the nature of words' meanings. It can be broken down into a variety of branches, including formal semantics, which studies the direct aspects related to meaning, such as sense, implication, and reference; lexical semantics, which studies word meanings and word relations, and conceptual semantics, which studies the evolving nature of meaning on a cognitive level. There are other sub-sections in which semantics can be broken into, but at the end they all come together to discuss to analyze the meaning of words in writing and speech and the way they come together towards one meaning.
Some of the best authors in literature and film utilize their writing to allow the reader to experience something that goes above and beyond a narrative or a theme or another direct concept. Authors are trying to persuade you, influence you, and eventually come to an agreement with their mindset or at least understand a certain complex idea .The word choice, placement, and context culminate into something greater than the sum of its parts. One of the best examples I can easily discuss from the top of my head is Cormac McCarthy. He is mostly known to the average person for the film adaptation of his novel, No Country for Old Men, but that piece is only one of the many examples one can bring up to analyze the nature of semantics in his prose.
Cormac McCarthy is commonly associated with westerns and other works that share similar themes with the genre. He deftly uses this genre's direct connections with the American form of the English language to not only break down the conventions and expectations the average English speaker might have with his word use, but also to properly explore its evolving nature in the larger scope of society as a whole. His last three works: The Counselor, No Country for Old Men, and The Road, are all amazing examples through which one can see an amazing use of semantics in a variety of ways.