An accusative flag is a °flag that marks a °nominal as °P-argument (in a °transitive clause), but not as °A-argument or °S-argument.
(1) This function need not be the only function; such flags commonly also express temporal extension (e.g. German eine-n Tag [one-ACC day] ‘for one day’), or the R-argument in a ditransitive clause.
(2) In many languages, only some of the P-arguments are marked by an accusative flag, in particular those with relatively high prominence (“differential object marking”).
accusative category (STR) = the morphosyntactic category in the accusative alignment system that exclusively expresses the P role. Example: the English accusa- tive pronoun forms me, him, her, us, and them are used only for the P role (the S and A roles use the nominative forms I, he, she, we, and they), and represent the accusative flag (morphologically manifested in English as base modification). (Section 6.3.1)