Estados Unidos = EE.UU. Why not E.U.?

This is a common question I get. The answer is very simple.

In Spanish, when we want a word to be “initialized” (for the sake of this explanation we are going to assume that “to initialize” means “to write the initials of a word”), we have to use double letter if the word is in plural. See the examples below:

  • Estados Unidos  EE. UU.
  • Naciones Unidas NN. UU.
  • Relaciones Públicas RR. PP.
  • Recursos Humanos RR. HH.
  • Servicios Higiénicos SS. HH.

That was a short and easy explanation to give.

Taken from Keeping Spanish Simple.