It is conventional in applied mathematics, computer science, and statistics to refer to a Boolean-valued function like " ? " " L " as a " k "-place interpretations of some " k "-place predicate symbol.
22.
Again, we might define a first-order language "'L "', as consisting of individual symbols a, b, and c; predicate symbols F, G, H, I and J; variables x, y, z; no function letters; no sentential symbols.
23.
Alfred Tarski ( 1951 ) proved that the theory of real closed fields in the first order language of partially ordered rings ( consisting of the binary predicate symbols " = " and " d " ", the operations of addition, subtraction and multiplication and the constant symbols 0, 1 ) admits elimination of quantifiers.
24.
On the other hand, a non-logical predicate symbol such as Phil ( " x " ) could be interpreted to mean " " x " is a philosopher ", " " x " is a man named Philip ", or any other unary predicate, depending on the interpretation at hand.
