By convention, relation constants also begin with either lower chase characters or digits. Each relation constant has an associated positive integer, called its arity . The type of each such word is given in the vocabulary specification. A vocabulary specification is a set of BNF rules defining the variables, object constants, and relation constants of a language. Terms A term is either a variable or an object constant.
Relational sentences are analogous to simple sentences in natural language.
The arguments of a conjunction are called conjuncts . The arguments of a disjunction are called disjuncts . The left argument of a reverse implication is the consequent . The right argument of an implication is called the consequent . The other arguments in both cases are called antecedents .