Plain verbs are phonologically specified for a certain hand configuration, a particular place of articulation and a specific path movement. The characteristic definition of plain verbs also accounts for plain verbs in DGS. Hence, they cannot be spatially modified to show manual agreement with their syntactic arguments, i.e. subject and/or object. From a phonological perspective, there are no clear-cut phonological criteria that identify plain verbs. Although many plain verbs, such as like, know or understand, are body-anchored, this is not a sufficient criterion to classify plain verbs. Plain verbs can also be articulated at the non-dominant hand in neutral signing space (buy), or in neutral signing space without body contact (play), as can be seen in the following example.
a. like
b. buy
c. play
A similar example is the verb cook that is not body-anchored, but lexically specified for the place of articulation in neutral signing space. Since the path movement of the sign is also lexically specified (the movement reminds of stirring in a pot), the sign cannot be modified to show manual agreement with its syntactic arguments.
cook
A further approach to identify plain verbs is by their argument structure [Syntax 2.1.]. That is, whether the verb requires only a subject to be grammatically correct or whether the verb also needs a direct and/or indirect object. The assumption would be that all verbs requiring only a subject, i.e. intransitive verbs (e.g. sleep, think or swim), are plain verbs, whereas all verbs that also need an object (e.g. visit, ask or drive) are either agreement verbs or spatial verbs. However, this constraint is also not sufficient to classify all plain verbs. Indeed, it is the case that the intransitive verbs sleep, die or laugh are plain verbs and that they can be body-anchored (laugh) as well as not body-anchored (die). But, there are also many plain verbs, which are transitive verbs and require a subject as well as an object (e.g. play, trust, buy, cook or repeat). These can also be body-anchored (trust) as well as not body-anchored (play). In conclusion, the argument structure of a verb is not a sufficient criterion to identify plain verbs. But a valid rule is that those verbs, which require a subject, a direct object and an indirect object, i.e. ditransitive verbs like give, order or show, cannot be plain verbs but are agreement verbs in DGS.
a. Intransitive verbs (sleep, think, swim, die, laugh)
b. Transitive verbs (not plain verbs) (visit, ask, drive)
c. Transitive verbs (plain verbs) (play, trust, buy, cook, repeat)
d. Ditransitive verbs (agreement verbs) (give, order, show)