linguistic:translation
A symmetric relation is a type of binary relation. Formally, a binary relation R over a set X is symmetric if:
  - ∀ a, b ∈ X, where the notation aRb means that ∈ R. An example is the relation "is equal to", because if a = b is true then b = a is also true. If RT represents the converse of R, then R is symmetric if and only if R = RT. Symmetry, along with reflexivity and transitivity, are the three defining properties of an equivalence relation.