predikátumkifejezéseknél

Predikátumkifejezés, or predicate expression, is a concept in logic and computer science. A predicate is a symbol that denotes a relation on a domain and may take one or more arguments. The arity of a predicate is the number of its arguments. A predicate application, written as P(t1, ..., tn), is an atomic formula whose truth value depends on the interpretation of P and the values of the terms t1 through tn.

In first-order logic, formulas are built from such atomic formulas using logical connectives and quantifiers; sentences have no free variables. A structure or interpretation assigns to each predicate symbol a particular relation on the domain, determining which instances satisfy the predicate. Predicates can be unary, binary, or of higher arity, and they can be combined with variables and function symbols to form complex conditions. The truth of a predicate application may depend on the values assigned to its variables, and these variables can be bound by quantifiers such as for all (∀) and exists (∃).

Outside pure logic, predicate expressions appear in programming and query languages as boolean conditions used in if statements, filters, or search queries. They guide control flow and data selection by evaluating to true or false for given inputs. Common examples include tests like P(x) meaning “x has property P” or relational predicates such as x > y, or Even(n) for an integer n. Predicates thus connect abstract logical meaning with practical decision-making in algorithms and data processing.