In all known natural languages, every noun in any given sentence will fill a certain
role in the way it relates to the action described by the verb.
Most verb phrases require at least two roles to be filled, namely the subject or agent,
the noun performing the action, and the direct object or patient, the noun receiving the
action, and some verbs may also require an indirect object or beneficiary of the action.
The words in the phrase that fill these mandatory roles are called arguments, while most other
roles will just provide extra optional information that’s not essential for the phrase to make
sense and are instead termed ‘adjuncts’.
It’s critically important then for a language to have a means of making clear what any given
word’s role is, otherwise phrases will be impossible or at least very difficult to interpret.
Across all known natural languages, there are three main ways this role-marking can
be done: The most common is to have a default word
order, so the nouns’ roles can be gleaned from their position in the sentence.
About 87% of languages sampled by The World Atlas of Language Structures have a default
word order of some kind, though there is considerable variation in word order patterns between,
and sometimes within, individual languages.
However, using word order alone is comparatively rare as a role-marking strategy, as it’s
most often complemented with one of the two other role-marking mechanisms: About 60% of
surveyed languages make use of grammatical case, wherein each noun is explicitly marked
for its role by means of an affix, while around 80% of languages employ verb agreement,where
the verb is marked with affixes that agree with at least one of the arguments in person,
number, and/or gender, allowing the listener to infer who’s doing what to whom based
on the verb’s inflection.
Some languages only mark the subject on the verb, which is the case for most European
languages, a very small number of languages mark just the object, usually as a result
of ergativity or some other complications pertaining to morphosyntactic alignment, but
more than half of all languages with verb agreement mark both the subject and the object
and occasionally the indirect object or other roles as well, a phenomenon called polypersonal
agreement.
Verb agreement most often evolves when pronouns become phonologically dependent on the verb
and are then incorporated into it to become affixes, at which point the verb cannot occur
without them.
This means that in languages with polypersonal agreement, most often the verb will be given
one set of affixes to mark the subject and a separate set for the object, and they’ll
usually come in the same or a similar order relative to each other and the verb as they
did before they were incorporated, although once polypersonal agreement evolves, it often
allows for increased word order flexibility.
Since the pronouns are already expressed on the verb, their roles can be inferred even
if they’re entirely omitted from the sentence.
Languages that routinely exclude pronouns in this way are called pro-drop languages,
and although not all pro-drop languages exhibit verb agreement, the extra information provided
by verb agreement makes pronoun-dropping especially likely.
Very often in pro-drop languages, including the pronoun serves to place focus on it or
to highlight its role in the phrase.
Somewhat related to pronoun dropping is the cross-linguistic tendency for a third person
singular subject to not be marked overtly, but instead to be inferred from a lack of
marking.
Basically, unless anything suggests otherwise, the default assumption is usually that the
subject is third person.
The plurality of the verb arguments is most often inherently expressed with the person
markers, since they derive from pronouns that already reflect grammatical number.
But some polypersonal languages also mark the plurality of either one or both of the
arguments elsewhere on the verb as well, a feature that sometimes gets called “verbal
number” or “pluractionality”.
In languages like Classical Nahuatl, the verb takes additional plural marking only for the
subject, while in others, like Navajo, the verbal plural marker can signify either a
plural subject or plural object or both depending on context.
Pluractionality most often evolves from frequentative or distributive aspect marking, signifying
that the verb happens multiple times, which then becomes inextricably associated with
the verb having multiple participants, and so the marking is reanalyzed as a sort of
verbal plural.
As for the person-markers themselves, In most polypersonal languages, the subject and object
affixes will come in a consistent order, and which marker refers to the subject and which
refers to the object will be interpreted from their position in the verb template.
But occasionally, certain combinations of subjects and objects will be encoded simultaneously
with a single inseparable affix that’s often not phonologically or etymologically related
to the expected subject and object markers.
This is called portmanteau agreement, and while there’s still research being done
into how exactly this comes about, there is some evidence that it evolves when more general
person markers take on additional implications of meaning, such as how in Guaraní, the portmanteau
marker that simultaneously encodes a first person plural subject and a second person
singular object seems to have evolved from an extended use of the intransitive first
person plural Inclusive subject marker.
Basically “You and I do something” got reinterpreted as “We do something to you”.
And for one final variation on polypersonalism, let’s talk about direct-inverse systems.
In these systems, the positions of the subject and object markers don’t conform to any
pre-determined order in the verb template, but instead according to what’s called a
person hierarchy, which in all attested cases has either 1st or 2nd person at the top, then
3rd person below those, and then any other persons the language might distinguish, like
inanimate or obviate 3rd person, at the very bottom.
Each of the persons included in the hierarchy will have an invariable slot in the verb template,
regardless of the role they play in the phrase, which means the identity of the subject and
object can’t be inferred from the person marking alone.
Instead, the default assumption is that it’s the argument higher on the hierarchy doing
something to the argument lower on the hierarchy, and if this isn’t the case, then a special
“inverse marker” is added to the verb to let the listener know the expected roles
have been reversed.
So how does this sort of system evolve?
The answer has to do with salience and animacy.
There’s a prevalent cross-linguistic tendency for languages to place greater focus, either
grammatically or syntactically, on animate arguments rather than inanimate ones, which
makes sense considering that humans generally like to talk about one another, and that inanimate
objects don’t really have any agency of their own or any ability to carry out any
independent actions.
This is exemplified by languages like Blackfoot, in which inanimate nouns are simply forbidden
from serving as subjects of transitive verbs, and by languages like Navajo, wherein the
nouns in a sentence must come in order of animacy as dictated by a strict hierarchy,
and if this order doesn’t correspond to the order of the subject and object, then
the third person object marker changes to reflect this.
The person hierarchies seen in direct-inverse languages are an extension of this idea, with
animacy distinctions being made among grammatical persons as well.
The higher up on the hierarchy an argument is, the more “animate” it’s perceived
to be, and so the more likely it is to be the subject.
However, if, counter to expectations, the more animate argument isn’t the one performing
the verb, the language may make use of valency or voicing tricks, like for example the passive
voice, to keep the animate argument as the subject.
Over time, as the pronouns then get incorporated into the verb to become agreement markers,
the passive becomes a necessary and mandatory component of the role-marking system, and
so thereby becomes an inverse marker.
Those are just some of the ways verb agreement can manifest, but marking roles solely through
verb agreement may open up a few ambiguities that might need be clarified with other strategies.
One common issue that arises is how to interpret the verb if both arguments are 3rd person.
In such a case, how do you tell who’s the subject and who’s the object?
One way to clear this up is to rely on grammatical gender.
If the person-marking on the verb agrees with the arguments in gender as well, then as long
as the arguments have different genders, it will still be clear who’s doing what to
whom.
A very common distinction to make is in animate versus inanimate arguments, As already mentioned,
most of the time subjects will be animate and objects inanimate, and so this distinction
may present itself in person-marking.
A language like Swahili takes this to a greater extreme, having around 18 different noun classes,
each having a unique verb agreement prefix, so most of the time the identities of the
subject and object are abundantly clear.
Alternatively, another strategy for disambiguation is obviation, which involves two different
3rd person markers, one for the proximate argument, or the one that’s most central
to what’s being discussed, and one for any other 3rd person arguments, which are termed
obviate arguments, which are either less relevant than the proximate argument or are considered
background information.
Obviation may be marked on the verb or the nouns or both.
Obviation is very strongly correlated with direct-inverse systems, as can be seen in
the Algonquin languages like Plains Cree and Ojibwe, which also have an animacy distinction
on top of obviation to further minimize ambiguity.
Finally, a language with verb agreement may clarify roles by simultaneously using either
of the other two role-marking mechanisms, word order or noun case.
As mentioned earlier, the majority of the world’s languages have a default word order,
and even though having a different role-marking strategy allows for some extra flexibility,
it’s still handy to have a default word order to disambiguate things if necessary.
Classical Nahuatl primarily uses polypersonal agreement to clarify roles and therefore allows
the constituents of a phrase to come in pretty much any order the speaker wants, but if any
ambiguity arises, it falls back on a default order of Verb-Subject-Object, while Swahili
still uses a consistent Subject-Verb-Object word order despite its pervasive person and
gender marking.
Combining verb agreement with noun case is a little bit rarer, but it’s fairly common
in European languages like Greek and Latin, which mark the subject on the verb, but also
have a robust case system while keeping word order pretty flexible.
It’s also interesting to note that many of the Romance languages that descend from
Latin have lost the case system outside of personal pronouns, but have compensated for
it with a much stricter word order.
Having both noun case and polypersonal agreement is quite rare, but can be seen in languages
like Basque and Georgian, the latter of which also has a fairly consistent word order as
well!
All languages are redundant to some extent, and so may end up double-marking one or more
roles to reinforce meaning.
For your own conlang, feel free to use a mix these strategies to employ as much or as little
role-marking as makes sense, so long as it’s always at least reasonably clear who’s doing
what to whom.
So, in summary, if you want to create a conlang that features verb agreement: Decide which
roles are going to be marked on the verb, whether it’s the subject, object, indirect
object, and/or other roles.
Incorporate pronouns into the verb complex to become agreement morphology.
Determine any additional morphology the paradigm may include, such as pluractionality, portmanteau
agreement, or inverse marking.
And decide what other role-marking strategies may be used to eliminate ambiguity.
Overall, verb agreement presents the possibility for a wide variety of unique and interesting
grammatical features, and can serve as a very useful tool for any conlanger’s repertoire.