initial
US /ɪˈnɪʃ.əl/
UK /ɪˈnɪʃ.əl/

1.
inicial
the first letter of a name or word, typically a person's first name or a significant word in a phrase.
:
•
Please write your initials at the bottom of the form.
Por favor, escriba sus iniciales al final del formulario.
•
Her necklace had her boyfriend's initial on it.
Su collar tenía la inicial de su novio.
1.
rubricar, firmar con iniciales
mark (a document) with one's initials, typically as a sign of approval or to indicate that one has read it.
:
•
Please initial each page of the contract.
Por favor, rubrique cada página del contrato.
•
She initialed the changes to confirm her approval.
Ella rubricó los cambios para confirmar su aprobación.