A specialization of functional predicate (q.v.) whose instances are those predicates that are in a strict sense functional in at least one argument-place (see Strictly Functional In Args and Single Entry Format In Args). That is, given any sequence of legal arguments placed in such a predicate's other argument positions, there is at most one argument such that, when it is placed in the predicate's functional position, the resulting formula is true. More precisely: Suppose PRED is an N-ary instance of functional predicate that is functional in its Kth place. Given any (N-1)-tuple consisting of things that are, respectively, legal arguments for (i.e. satisfy all argument-constraints on) the N-1 argument-places in PRED other than its Kth-place, there is at most one thing -- call it O(K) -- such that (PRED O(1)..O(N)) is true. For example, biological mother is functional in its second argument-place, since every animal has one and only one biological mother. Note that it might be the case that, for some ways of fixing PRED's other arguments, there will be _nothing_ that would yield a true formula when put into PRED's functional argument-place; for example, while a country has at most one dictator (see Dictator), some countries have no dictator. A binary strictly functional predicate that is strictly functional in its second argument is an instance of predicate that is strictly functional in its second argument (q.v.).