Morphosyntactic alignment is about how the different core arguments of a verb are grouped into cases (wether these are explicitly marked or not is irrelevant. Well... most of the time, anyways*). Let's take a look at the different kinds of core arguments:
S: Subject (sometimes Experiencer) of an intransitive sentence
A: Agent of a transitive sentence
P: Patient of a monotransitive sentence
R: Receiver of a ditransitive sentence
T: Theme of a ditransitive sentence
Intransitive: He (S) sleeps
Monotransitive: He (A) hits her (P)
Ditransitive: He (A) gives her (R) a book (T)
Let's look at the grouping of S, A, and P first.
- Accusative languages group S and A into the nominative. P becomes the accusative. f.e. English
- Ergative languages group S and P into the absolutive. A becomes the ergative. f.e. Basque
- Tripartite languages assign a different case to each: S is the intransitive, A the ergative and P the accusative. f.e. Wangkumara
- Active languages (sometimes called split-ergative) group S with P or with A, depending on an external factor. This can be wether S is in control or not, wether the verb represents a state or an action, ... or it can be completely arbitrary. The two resulting cases are commonly called agentive and patientive, but also ergative and accusative respectively. f.e. Georgian, sometimes
- Some other languages exhibit even weirder alignments, like an animacy hierarchy (aka direct/inverse system). I'm not sure about this, but I think I even read about a language which groups A with P and marks S differently. Which is pretty damn crazy.
Now let's look at the grouping of P, R and T. This part of alignment usually receives less attention... a pity, really.
- Dative languages (or direct/indirect-object-languages) group P with T. R becomes the dative. f.e. English
- Dechticaetiative languages (or primary/secondary-object-languages) group P with R. T becomes the dechticaetiative. f.e. Yoruba
- There are also languages that group P, R and T in a single case, and rely completely on context in ditransitive sentences to make out which is which.
English is accusative-dative.
Basque is ergative-dative.
Yoruba is accusative-dechticaetiative.
My own language, Lembrin is (semantically and syntactically) active-dechticaetiative.
It makes a control-based distinction in intransitive sentences between agentive and patientive. It is also Fluid-S which means that you aren't forced to use one of them, you can use both and get subtle differences in meaning:
I run (and I am in control)
I run (and I am not in control)
One could say this when being chased, or something.
The opposite is Split-S which means that you have to use the agentive with some verbs, and the patientive with others.
Lembrin is dechticaetiative:
oi dauma lis stymo
you-PAT give-VRB I-AGT chair-DCH
I give you the chair
On top of that, Lembrin has a few verbs which are semantically monotransitive, but syntactically behave like ditransitive sentences with either the agent or the patient missing. An example is cør, to agree with. The subject is in the agentive or the patientive, depending on control, whereas the object is in the dechticaetiative:
cøra lis réasso
agree-VRB I-AGT document--DCH
I agree with the document (and I am in control)
li cøra réasso
I-PAT agree-VRB document--DCH
I agree with the document (and I am not in control)
One could say this when one is forced to sign it, for example.
So, what's your language's morphosyntactic alignment?** You are encouraged to draw a diagram and provide examples
*: Some languages show different alignments morphologically and syntactically.
**: I realise that this question is perhaps a bit oversimplified: some languages show different alignments depending on other factors like verb tense, 1st, 2nd or 3rd person, ... in that case, feel free to elaborate