<*logic*>
an operator (i.e. something which if added to one or more
propositions makes a (molecular) proposition) is
non-truth-functional iff the truth value of a proposition
in which it appears is not wholly determined by the truth value of
the subsiduary propositions on which it operates. E.g. the truth
value of "it is necessary that there are nine planets" and "it is
believed that there are nine planets" is not determined by the
truth value of "there are nine planets." Hence the operators "it is
believed that" are non-truth-functional operators.
truth-functional

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