Some verbs are semantically classified as transitive, yet they can form a grammatical clause with a single argument distinct from the agent. This unique argument is coded as U. This parameter considers exclusive word order, which refers to the relative positions of the verb (V) and its unique argument (U). To constitute a unique-argument construction, a (declarative) sentence must meet the following criteria:
- V only requires a non-agent as an argument (U).
- In other constructions, U generally functions as P (patient) or R (recipient or beneficiary).
- U is semantically unmarked.
No distinction is made necessary between basic and dominant exclusive word order, since they rarely diverge. If two word orders are possible, the dominant word order can be determined based on the following rules:
- If neither occurs at least twice as frequently as the other, there is no dominant word order.
- If one word order occurs at least twice as frequently as the other, it is considered the dominant word order.
NoUWO: Unique-argument constructions with transitive verbs are not possible.
VU: The exclusive word order is VU.
UV: The exclusive word order is UV.
When a language displays both word orders, both values can be listed. If one type 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.
 These “impersonal transitive” constructions feature only the patient, recipient, or beneficiary as an argument; expression of the agent is impossible. See the Latin Taedet me ‘I am disgusted’ (lit. ‘[it] disgusts me’), Russian, Jemu vezjot ‘He is lucky’ (lit. ‘for him [it] leads’), and Finnish Minua nukuttaa ‘I am sleepy’ (lit. ‘[it] makes me sleepy’). The majority of the languages of the world lack this type of construction.
 If the order of U and V is affected by semantic or grammatical features, the exclusive word order is based on the relative positions of U and V in an unmarked sentence. If word order is affected by definiteness, for example, a sentence featuring an indefinite argument should be considered.
 For example, VU / UV means that the dominant exclusive word order is VU, but there are instances of UV, too.