A lexicon is essentially a collection of words and their meanings, similar to a dictionary. It can refer to the vocabulary of a specific language, a particular field, or even an individual. For example, the lexicon of medicine includes terms like "diagnosis" and "treatment," which may not be familiar to everyone. In addition to words, a lexicon can also encompass phrases and expressions used within a certain context. For instance, the lexicon of computer programming includes terms like "algorithm" and "syntax." Understanding a lexicon helps people communicate effectively within a specific area of interest or expertise.