The term locus refers to the place the of overt morphological marking of head/dependent relations. In a verb phrase, the head is the verb. Active transitive sentences should be chosen featuring an agent (the subject and agent in nominative sentences, generally marked as A) and patient (the direct object and patient in nominative languages, generally marked as O or P). Head marking is present if at least some types of agents or patients trigger agreement on the verb. If the marking of a language displays features of more than one type, the data should be examined to determine if one type emerges as dominant. (For example, if the head/dependent-marking pattern differs for nouns and pronouns, the type characteristic of nouns is considered dominant.) If dominance cannot be determined, the language features a split system, which is marked with the use of an ampersand (&) between the two parameter values.

Types:

NoVDepMk: Neither the agent nor the patient is marked; the verb does not show morphological agreement with either.

VMk[A]: The agent is not marked as such, but it is marked on the verb. (Agreement is shown only with the unmarked agent.)

VMk[O]: The patient is not marked as such, but it is marked on the verb. (Agreement is shown only with the unmarked patient.)

VMk: Neither the agent nor the patient is marked, but they are both marked on the verb. (Agreement is shown with both the unmarked agent and the unmarked patient.)

DepMk[A]: The agent is marked as such; it is not marked on the verb.

DepMk[O]: The patient is marked as such; it is not marked on the verb.

DepMk: The agent and patient are marked as such; they are not marked on the verb.

VDepMk[A]: The agent is marked as such; it is also marked on the verb. (Agreement is shown only with the marked agent.)

VDepMk[O]: The patient is marked as such; it is also marked on the verb. (Agreement is shown only with the marked patient.)

VDepMk[ANonO]: The agent is marked as such, while the patient is not. Both the marked agent and the unmarked patient are marked on the verb. (Two-way agreement is shown; the patient is unmarked.)

VDepMk[ONonA]: The patient is marked as such, while the agent is not. Both the unmarked agent and the marked patient are marked on the verb. (Two-way agreement is shown; the agent is unmarked.)

VDepMk: Both the agent and the patient are marked as such; both the marked agent and patient are marked on the verb. (Two-way agreement is shown with two marked arguments.)

VDepFlMk: The marking of the agent and patient is flexible. (For example, the patient is marked by a morpheme that attaches to the word directly before, regardless of what that word may be.) This is known as floating (or free) marking.

When a language displays more than one strategy, two values can be listed. If one strategy is dominant, a slash (/) can separate the two values, with the dominant value appearing first; if neither is dominant, they are listed with an ampersand (&) separating the two. The use of parentheses indicates that the strategy is not obligatory.

1 Differences in word order do not constitute morphological marking. Word order may be fixed, regardless of parameter value. Zero morphemes constitute morphological marking if they contrast with overt morphemes in the rest of the paradigm.

2 For example, if the verb shows overt agreement with only definite objects, this constitutes objective agreement. The seeming lack of agreement on indefinite objects should also be considered a form of agreement, since it conveys information about the object (that it is not definite).

3 For example, the value VMk&VMk(A) indicates that objective agreement is optional. Parameter values of the type should be accompanied with an explanation in the commentary.

4. An agent marked by a zero morpheme should be considered unmarked. A marked agent displays explicit morphological marking.