A "relation" refers to the way in which two or more entities are connected or associated with each other. This can include various types of connections, such as familial ties, friendships, or professional associations. For example, a brother and sister have a familial relation, while colleagues at work share a professional relation. In mathematics, a relation describes a relationship between sets of values. For instance, a relation can connect elements from one set, like students, to another set, such as grades. This helps in understanding how different elements interact or correspond with each other in a structured way.