Locus classicus is a term used in academic writing to refer to a passage, argument, or example that is considered a classic and authoritative representation of a particular concept or idea. Synonyms for locus classicus include a touchstone, archetype, paradigm, archetype, or exemplar. These words are often used interchangeably to indicate a fundamental source of inspiration or authority in a particular field. For example, a classic book like "To Kill a Mockingbird" can be considered a locus classicus of American literature. Similarly, a mathematical equation like Pythagoras' theorem can be called an exemplar of geometric principles.