NoSMark: The function S is not explicitly marked, while P, A, or both are marked. S is therefore marked with a zero (∅) morpheme.
(1) (én) énekel-ek.
(2) (én) level-et ír-ok.
I letter-acc write-prs.1sg
‘I’m writing a letter.’
In Hungarian, if the noun is in the A (1) or the S (2) position, it is unmarked, while the P takes the accusative suffix (2). From a formal perspective, the grammatical subject (S/A) is identifiable by its nominative case marking and by the agreement of the verbal morphology (cf. Tolcsvai Nagy 2012, 2013: 283‒312, É. Kiss 2002: 8‒14).