ABSTRACT
A dyadic relation holds not simply between a pair of objects, but between those objects in a certain order. It is one thing to say that Bill is father of Tom, and another thing to say that Tom is father of Bill. Analogous considerations apply to relations with more places than two. There are, however, many expressions which we cannot meaningfully apply to single objects, but only to groups of two, three or more objects. Up to now, all the expressions we have called predicates have stood for properties which it makes sense to attribute to a single individual. Such predicates are known as monadic, or one-place, predicates.
