(a). Accusative of direction.—To show direction towards which movement (physical or otherwise) is made the accusative is used, and this is generally called "the accusative of direction." It will be observed, however, that we can also use a preposition to show the motion, and, if such preposition in itself shows movement, its complement must be in the nominative, since all prepositions govern that case; but if the preposition does not in itself denote movement, then its complement must be in the accusative.
Examples.—Mi iras Romon (aŭ, al Romo) = I am going to Rome. Li kuris en la ĝardenon = He ran into the garden. The preposition en does not show movement, therefore ĝardenon is in the accusative, but Li kuris en la ĝardeno = He ran in the garden. This means he was already in the garden, and was running in it. Sur la danan tronon mi havas rajtojn = On the Danish throne I have rights.
(b). Adverbs also take the accusative of direction.
Examples.—Kien vi iras? Mi iras nenien hodiaŭ = Where (whither) are you going? I am going nowhere to-day. Ĝi falis teren (or, sur la teron) = It fell to the ground (or, on to the ground; lit., earthwards). Li iris hejmen kaj restis hejme = He went home and remained at home.
68. (3). To show that a preposition has been omitted.
As stated in Rule 8, par. [94], every preposition in Esperanto governs the nominative case.
By Rule 14 we are told that every preposition has a defined and constant meaning, but that if we must use some preposition, and the direct sense does not show what special preposition we are to take, we can then either use the indefinite preposition je, or the accusative without a preposition. The following are examples under this head in which the accusative may be used:—
(a). After doubtful verbs.—From the foregoing remarks it follows that if we do not know whether a verb governs the accusative or not, we can always use the accusative, if no ambiguity is occasioned thereby. Otherwise some preposition should be employed instead.
For instance, we can say:—Obeu vian patron, or, Obeu je via patro, or, Obeu al via patro = Obey your father. Ŝi helpis al sia frato, or, Ŝi helpis sian fraton = She helped her brother. Li pardonis sian filon, or, Li pardonis al sia filo = He forgave his son. But in phrases where doubt as to meaning may arise we must always use a preposition, as:—Li pardonis al sia filo lian kulpon = He forgave his son his fault. Not Li pardonis sian filon lian kulpon, for the two accusatives here would create confusion. Li legis tion en la dua de Marto, or, Li legis pri tio la duan de Marto = He read that on the 2nd of March.
(b). Duration or any point of time.