To verbs denoting a state, and to adjectives, an accusative may be added to denote a thing in respect to which the verb or adjective is limited.
a. The accusative usually expresses a local relation or the instrument. The word restricted by the accusative usually denotes
The accusative of respect is employed
a. Of the parts of the body:
ὁ ἄνθρωπος τὸν δάκτυλον ἀλγεῖ
τυφλὸς τά τ' ὦτα τόν τε νοῦν τά τ' ὄμματ' εἶ
N.—The accusative of the part in apposition to the whole ( cross985) belongs here, as is seen by the passive. Cp.
τὸν πλῆξ' αὐχένα
b. Of qualities and attributes (nature, form, size, name, birth, number, etc.):
διαφέρει γυνὴ ἀνδρὸς τὴν φύσιν
οὐδὲ ἔοικεν θνητὰ_ς ἀ_θανάτῃσι δέμας καὶ εἶδος ἐρίζειν
λέξον ὅστις εἶ γένος
c. Of the sphere in general:
γένεσθε τὴν διάνοιαν
τὸ μὲν ἐπ' ἐμοὶ οἴχομαι, τὸ δ' ἐπὶ σοὶ σέσωσμαι
ταῦτα ἀγαθὸς ἕκαστος ἡμῶν, ἅπερ σοφός, ἃ δὲ ἀμαθής, ταῦτα δὲ κακός
Very rarely after substantives: χεῖρας αἰχμητής
νεα_νίαι τὰ_ς ὄψεις
For the acccusative of respect the instrumental dative ( cross1516) is also employed, and also the prepositions εἰς, κατά, πρός, e.g. διαφέρειν ἀρετῇ or εἰς ἀρετήν.1604
Not to be confused with the accusative of respect is the accusative after intransitive adjectives ( cross1565) or after the passives of 1632.1605
The accusative of respect is probably in its origin, at least in part, an accusative of the internal object.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].