Differential Object Marking

Some languages, such as Russian, Turkish, Finnish and Hebrew, have a thing known as differential object marking. English, to some extent, can also be said to have it, although in a less predictable, unsystematic form.

In these languages, the direct object gets a different marking depending on some grammatical distinction. In Turkish and Hebrew, direct objects are normally marked identically to subjects, but when the object is definite, it is marked with an object marker. -yi|-yı|-yü|-yu in Turkish, et- in Hebrew.

In Finnish, the object is slightly more complicated, and the distinction that is made is not primarily one of definiteness. If the action is negated, the object is marked with the partitive case:

minä e-n siedä kylmää vettä

I not-1SG tolerate cold-PART water-PART

I can't stand cold water

This holds regardless of the aspect of the verb. If the verb is positive, and atelic, you also get the partitive:

aja-n auto-a

drive-1SG car-part 

I am driving (the|a) car

However, if the verb is telic and positive, the object is marked by the accusative:

aja-n auto-n auto-talli-in
drive-1sg car-ACC car-stable-INTO
I('ll) drive the car into the garage (implicitly, this is mentioned with the result in mind, or as something that will be completed before the speaker goes on to the next thing he's about to do)

hän rakentaa talon valmiiksi ensin

3SG build-(3sg) house-ACC ready-TRANSL first-INSTR

he will build the house (to completion) first*

* in the sense of 'before doing something else'

One context in which such completion is pretty central is when giving the order in which events are to happen:

syö-n ruoa-n ja sitten tule-n muka-an

eat-1sg food-ACC and then come-1sg with-TO

I'll eat food and then I'll come

c.f. the case marking in a less time-ordered utterance:

älä nyt, syö-n ruoka-a

don't_IMPER now, eat-1SG food-PART

stop doing that, I'm eating food

So basically, when the completion of the action is relevant, and it is a positive utterance, it's accusative, otherwise it is partitive. There's further complications with regards to the marking of the accusative, but that is syntactically predictable. 

Other similar systems exist in languages around the world, and looking at one particular part of English grammar might be relevant.

C.f. 

I shot the bear vs. I shot at the bear

The former implies that the bear, in fact, was hit (and probably died), whereas the latter tells us that the shooting was a failure. Many English verbs seem to have similar pairs, where the prepositionless version is more telic and successful, whereas the version with the preposition generally is less telic, less successful. However, different verbs seem to have different prepositions in use, and just a few exceptional ones seem to have the opposite situation - a preposition makes the verb more telic, c.f.

eat vs eat up

 However, in English, some of these verbs permit this even without an explicit object, so whether it's object marking or just 'marking' is a bit unclear.

Ergativity

For ergativity, we need to introduce a few other concepts.

Transitivity

A transitive verb is a verb that has both a subject and an object. Examples:

I see her.

Subject in italics, object in bold. The notion of transitivity is not entirely uniform - there's syntactic transitivity, which is pretty much "is there a direct object present (or at least marked for or strongly implied)", and semantic transitivity, which seems way more fuzzy around the corners.

It might seem weird to consider 'I shot it' to be transitive, but 'I shot at it' not to be transitive. Languages may differ in how they understand such constructions - verbs may have adpositions as 'integral' parts, and then 'shot at it' would be transitive; English seems to have some phrasal verbs to be integral, some not. Who knows, really.

Anyways, an intransitive verb is a verb that does not have a direct object.

We can now go on and consider subjects.

Ergativity

Ok, so we have a transitive verb:

I see her.

Let us call these A and P, agent and patient. And we consider what to do when we have a verb that only has one argument - we call it the undergoer, simply to provide a distinction. In English, undergoer is marked the same as agent:

I sleep.

However, in ergative languages, the undergoer gets the same marking as the patient:

I see her. Her sleeps 

Of course, this needn't only be present in the marking on nouns and pronouns, it can also be present in verb congruence and the like. I.e. we may have congruence only for the absolutive (the object or intransitive subject) argument, we may have congruence only for the ergative argument (the subject when there's an object present), thus giving patterns like:

I sees her.
her sleeps.
She am seeing me.
Me am sleeping
But
her is sleeping.
I is seeing her

However, congruence in some languages follow a nominative pattern despite having ergative case:

I see her
her sleeps
me am sleeping
her is sleeping
I am seeing her

 

Case

Case is a somewhat complicated issue, because it is a term that is quite polysemous - it signifies quite distinct things when used at quite distinct levels of analysis. However, its primary use clearly is with regards to morphological case.

Morphological case notably appears in several classical languages - Latin, Greek, Sanskrit - but also in any number of modern languages - German, Finnish, Russian, Georgian, Turkish, etc.

Classically, case is a morphological way of marking the role a noun (or other noun-like word) has in the sentence. For instance,

Jaakko	ost	-i	auto	-n
Jaakko(NOM)	buy	-PAST	car	-GEN

Jaakko-n  auto-sta soi musiikki-aJaakko-GEN  car-ELA ring music-PART

Jaakko osti auton, Jaakko bought the car. From Jaakko's car there is music playing. In this case in Finnish, the singular genitive is identical in form to the singular accusative, the genitive also serving a role similar to English -'s. In comparison

Иаков купил машину

Yakov bought car-acc

-у is almost exclusively used for feminine accusatives, and masculine and neuter datives. Anyways, quite obvious. Affixes mark case, and we can list them like, say, Finnish: auto, auton, autoa, autossa, autolla, ... We know from Latin and Russian that a case needn't be distinct throughout the paradigm to qualify as a distinct case: Russian conflates nominative and accusative for inanimate masculines and neuters, but distinguishes locative and dative for those; on the other hand, it conflates dative and prepositional for feminines. Latin likewise conflates some cases for some subsets of the noun system.

We can go on and look at some other 'popular' cases:

Jaakko anto-i kirje-en äidi-lle-si
Jaakko give-PAST.3sg letter-ACC mother-TO-2SG.POSS
Jaakko gave letter to your mother
Jaakko gave your mother a letter
Jaakko hat deiner Mutter einen Brief  gegeben
Jaako has your-FEM.DAT Mother one-ACC letter GE-given
Jaakko has given your mother a letter
Jaakko gave your mother a letter

The -si suffix in Finnish is not a case, really - it's more like English 'your', but tacked on to the noun. This is known as a possessive suffix. It is not a case since it does not tell us anything about the syntactic role of the noun. We can see this is not a case, since if we replace it by any other suffix out of the same set, we have not changed the role of the mother, we have only changed whose mother it is - however, if we change -lle-, we go and alter what role she has in the sentence. äidiltäsi, for instance, would code for 'from your mother', and some cases would simply make the sentence unparseable.

In German, very few cases are marked directly on the noun. Generally, case marking goes on adjectives and articles. Case, ultimately, more often is relevant on a phrasal level, not a word-level. I.e. when we say he bought a big red car, if 'car' were marked for some case, it'd generally reflect the role that the whole phrase a big red car has in the context. Therefore also, some languages mark other constituents as well, c.f. how Finnish would render it:

hän osti iso-n punaise-n auto-n

In both of the examples above, 'mother' is marked with the case that in that language marks the recipient of an action. In Finnish, this also marks the destination of a movement (and more specifically, a destination external to the noun so marked). In German, the dative is not used for destinations, but more often to mark that the preceding preposition marks position rather than destination.

What do cases do? Well, a lot of the same roles that prepositions do in English, but also some other roles. English has about three cases - nominative (nouns in singular and plural, I, you, he, she, it, we, you, they), genitive (-'s, -s') and some kind of oblique/accusative/dative for pronouns (me, you, him, her, us, you, them, whom). We may notice that objects in English are nominative for nouns and several pronouns (anyone, someone, etc), but accusative for those pronouns that I listed above. Same goes for indirect objects. Some languages have separate markers for those. Some languages also have separate prepositions for such roles, c.f. also English 'to' as an indirect object marker. The Spanish object marker a may serve as an example here.

However, some languages also distinguish the functions of an adposition by different cases. Examples of such languages are German, Russian and Latin. So for instance, в(о), /v(а)/ signifies 'in' with the noun in the locative and 'into' with the noun in the accusative in Russian.

Next up: differential object marking (or ergativity?)