Passive

Passive is a construction in which the logical object shows up as the grammatical subject, while the logical subject is not expressed at all or shows up in an adjunct by-phrase.

Example
(ii) is the passive counterpart of active (i).

(i) Civil servants should avoid passive constructions (ii) Passive constructions should be avoided (by civil servants)

In GB theory
The standard view in GB-theory is that in a passive configuration the external theta-role (=logical subject) is assigned to the participial morpheme (-ed of avoided in (ii)), and that as a consequence the subject position is a theta-bar position. In order for its theta-role to be licensed, the participial morpheme also absorbs the structural objective case of the base verb. This leaves the object, which is generated at D-structure in complement position and receives the internal theta-role just as in active sentences, without Case. The object then moves to subject position where it receives nominative Case (i.e. becomes the grammatical subject). Next to this derivational account, lexical analyses of passive have been proposed, which take the promotion of the internal argument to be a consequence of the interaction of lexical rules deriving the argument structure of complex words and the specific lexical properties of the passive morpheme. Languages vary with respect to the ways of forming a passive; sometimes it is not even clear whether a given construction is to be regarded as a passive or not. This is because passive is in fact the sum of a cluster of properties (logical object as subject, logical subject as optional adjunct, passive morphology on the verb, no Case assignment to the object possible, etc.), all of which can be separately present or absent in a given construction. Some main distinctions across languages are the following:


 * languages with impersonal passives (= passive of an intransitive verb, with an expletive in subject position instead of a promoted object) vs. languages without (cf. Dutch er wordt een man vermoord versus English *there is a man killed)
 * languages with periphrastic passives (i.e. using auxiliaries plus a past participle) vs. languages with synthetic passives (expressing the passive via one verbal form) (cf. Dutch de koning wordt geprezen vs. Latin rex laudatur)
 * languages with optional adjuncts expressing the logical subject vs. languages without (see by-phrase).

Links
Utrecht Lexicon of Linguistics