: something that is designated or expressed by a sentential function
First Known Use of PROPOSITIONAL FUNCTION
Sentencelike expression that may be thought of as obtained from a sentence by substituting variables for constants occurring in the sentence. For example, x was a parent of y may be thought of as obtained from Adam was a parent of Abel. A propositional function therefore has no truth-value, becoming true or false only when its free variables are replaced by constants of appropriate syntactic categories (e.g., Abraham was a parent of Isaac).