For native English speakers, the phrase “her jumped very high” sounds rather awkward. This is because “her” is usually used to refer to someone who is being affected by an action and not someone doing the action. Yet, as we’ll see below, this construction wouldn’t feel odd at all in languages such as Basque, Georgian, Warlpiri, or Inuktitut whose sentence structures vastly differ from those of English.

In many languages, words change forms to indicate a change in meaning or to clarify what role they play in a sentence. These different forms are referred to as cases and this pattern of marking cases as a way to structure sentences can be described as morphosyntactic alignment. Morphosyntacic alignment is simply a form of grammatical relationship in language that is used to explain how these core arguments of a sentence are positioned and placed in relation to their features. While these relationships can be distinguished morphologically through case markings, they can also be distinguished syntactically through word order. 

To dive deeper into understanding morphosyntactic alignment, we must first define a few key terms. 

Firstly, the subject (often represented by an S) refers to the sole actor in a one-person event, or the sole argument of an intransitive verb — for instance, “Jane” in “Jane walks” would be the subject of the sentence. 

Secondly, the agent (often represented by an A) refers to the argument of a transitive verb that serves as the actor of an action while object (often represented by an O) refers to the argument that serves as the patient, or recipient of the action. In a sentence such as “Jay bought candy”, Jay would be the agent while candy would be the object. 

Lastly, transitivity refers to the property of verbs that requires them to have an object. For example, the verb "brought" in "I brought pie" needs an object (in this case, "pie") to complete the sentence. In contrast, intransitive verbs like "lied" don’t require an object, as can be demonstrated in the sentence "he lied."

Now, we can delve into various different systems of morphosyntactic alignment. 

➢ The nominative-accusative alignment. In this alignment, subjects of intransitive verbs and agents of transitive verbs receive the same nominative marking, while the object of transitive verbs receive a distinct accusative marking (S=A≠O). In the Latvian sentence, 

“bērns zīmē suni” (the child draws a dog), 

bērns is the agent of the transitive verb zīmē with a nominative marking while suni is the object with an accusative marking. In a clause with an intransitive verb such as “suns skrien”, suns would be used to refer to the dog as the nominatively marked subject. This alignment is “not only the dominant alignment overall but also in every major geographical area”. 

➢ The ergative-absolutive alignment. In this alignment, subjects and objects receive the same absolute marking while agents receive their own distinct ergative marking (S=O≠A). The awkwardness of “her jumped very high” mentioned above can attested to the fact that English utilizes the nominative-accusative alignment — this construction would be valid if English used the ergative-absolutive! Take these two sentences in Basque, for instance: 

1. “Liburua galdu da” (the book is lost) 

2. “Gizonak liburua galdu du” (the man has lost the book) 

Despite liburua (meaning ‘book’) appearing as the subject of the intransitive verb in the first sentence and the object of the transitive verb in the second, it is in the absolutive case across both examples.

While most languages don’t demonstrate complete ergativity like Basque does, and demonstrate some features of nominative-accusative forms often in word order (an alignment that is referred to as split-ergativity), ergativity is nonetheless actualized in various different grammatical forms amongst languages primarily located in South America, Southeast Asia, and Mesoamerica.

➢ The neutral alignment. In this alignment, there is no morphosyntactic distinction whatsoever between the subject, agent, and object (S=A=O). Languages possessing this alignment are exceptionally rare as lacking a clear morphological marking (that is, a change in the form of the word) isn’t enough; there must also be a lack of syntactic marking (that is, a change in the ordering of the words). In a neutral alignment system, the sentences “the boy pets the cat” and “the cat pets the boy” would look and function identically. This alignment when found is found most commonly in West Africa, the Caucasus, and South and Southeast Asia.

➢ The tripartite alignment. In this alignment, subjects, agents, and objects share no markings in common (S≠A≠O). Beyond the fictional Na’vi language from the Avatar franchise which exhibits the tripartite alignment, there are few languages that can be considered fully tripartite. Hokkaido Ainu, however, is an example a partial-tripartite language that utilizes this alignment in some aspects of their grammar; for instance, Hokkaido Ainu’s case markings for the first-person plural are -as for the subject of an intransitive verb, ci- for the agent of a transitive verb, and un- for objects. 

➢ Though rarer than these examples, there are a multitude of other morphosyntactic alignments not mentioned in this article that can be found across the languages of the world.

Though morphosyntactic alignment stands as an abstract subset of linguistics that is rather difficult to fully grasp, it still holds significant value in said abstractness. It allows us to generalize and compare languages around the world and figure out which features are universal (or not), allows us to find deeper insights into the cognitive processing of grammatical structures, and allows us to accurately demystify the different logics behind how sentences ought to be constructed.