What is a semantic field?

Semantic (or sometimes called lexical) fields are a technique often used by writers to keep a certain image persistent in their readers' mind. They are a collection of words which are related to one another be it through their similar meanings, or through a more abstract relation.

For example, if a writer is writing a poem or a novel about a ship, they will surely use words such as ocean, waves, sea, tide, blue, storm, wind, sails, etc... Again, it is a collection of words which relate to each other in a semantic (which means meaning) or abstract way.