How is it called when f(g(x)) = x?

There are a couple of function pairs which lead to the identity if applied after each other, e.g.

  • decrypt(encrypt(value)) == value
  • deserialize(serialize(data, filepath)) == data

How is this property called? Suppose one function undoes the property of the other one and it is guaranteed that this is possible for all values (within the domain of interest).