Everything about Transitive Relation totally explained
In
mathematics, a
binary relation R over a
set X is
transitive if it holds for all
a,
b, and
c in
X, that if
a is related to
b and
b is related to
c, then
a is related to
c.
To write this in
predicate logic:
»
For instance, the "greater than" relation is transitive:
» If A > B, and B > C, then A > C.
Examples
For example, "is greater than," "is at least as great as," and "is equal to" (
equality) are transitive relations:
» whenever A > B and B > C, then also A > C
whenever A ≥ B and B ≥ C, then also A ≥ C
» whenever A = B and B = C, then also A = C
For some time, economists and philosophers believed that preference was a transitive relation however there are now mathematical theories which demonstrate that preferences and other significant economic results can be modelled without resorting to this assumption.
On the other hand, "is the mother of" isn't a transitive relation, because if Alice is the mother of Brenda, and Brenda is the mother of Claire, then Alice isn't always the mother of Claire. What is more, it's
antitransitive: Alice can
never be the mother of Claire.
Then again, in biology we often need to consider motherhood over an arbitrary number of generations: the relation "is a
matrilinear ancestor of". This
is a transitive relation. More precisely, it's the
transitive closure of the relation "is the mother of".
More examples of transitive relations:
Closure properties
The converse of a transitive relation is always transitive: for example knowing that "is a
subset of" is transitive and "is a
superset of" is its converse, we can conclude that the latter is transitive as well.
The intersection of two transitive relations is always transitive: knowing that "was born before" and "has the same first name as" are transitive, we can conclude that "was born before and also has the same first name as" is also transitive.
The union of two transitive relations isn't always transitive. For instance "was born before or has the same first name as" isn't generally a transitive relation.
The complement of a transitive relation isn't always transitive. For instance, while "equal to" is transitive, "not equal to" is only transitive on sets with at most two elements.
Properties of transitivity
For a transitive relation the following are equivalent:
irreflexivity
asymmetry
being a strict partial order
Other properties that require transitivity
preorder - a reflexive transitive relation
partial order - an antisymmetric preorder
total preorder - a total preorder
equivalence relation - a symmetric preorder
strict weak ordering - a strict partial order in which incomparability is an equivalence relation
total ordering - a total, antisymmetric transitive relation
Counting transitive relations
Unlike other relation properties, no general formula that counts the number of transitive relations on a finite set is known. However, there's a formula for finding the number of relations which are simultaneously reflexive, symmetric, and transitive – in other words, equivalence relations –, those which are symmetric and transitive, those which are symmetric, transitive, and antisymmetric, and those which are total, transitive, and antisymmetric. Pfeiffer has made some progress in this direction, expressing relations with combinations of these properties in terms of each other, but still calculating any one is difficult. See also.
Further Information
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