The Real Spanish Academy and the Academies Association of the Spanish Language have a debt with the society to construct a dictionary of this type. The Spanish is the only western language that lacks an historical dictionary, essential instrument for the work of the Hispanists, as well as for the knowledge that Spanish-speaker have to have of their language.
Historical origin:
The forms and that combines with feminine words that begin by a or (ha) tonic are historically feminine, since it wass Latin origin also feminine illam (> ell> el(a)), unam (> un(a)). Therefore, it is necessary to speak of forms, masculine ones el, un (el niño, un niño), and other ones feminine (el alma, un alma).