Participial adjective
A word form which is identical in form to the participle but which functions as an adjective. Examples are: rolling stone, fallen leaf, burnt cat, rotten egg, missing persons etc.
Participial relative clause
A relative clause which contains a participle instead of a finite verb. In the following examples, the first sentence contains a participial relative clause, while the second sentence contains an equivalent full relative clause.
The boy sitting next to my wife is her nephew. (Here the participial relative clause is ‘sitting next to my wife’.)
The boy who is sitting next to my wife is her nephew. (Relative clause: who is sitting next to my wife)
Past perfect
The English construction in which had is combined with the past participle form of a verb. The past perfect is the past-tense form corresponding to the present perfect.
Sometimes the past perfect is used to express an unreal condition in the past. Example: If you had invited him, he would have come. Here the use of the past perfect ‘had invited’ indicates that you did not in fact invite him.
Perfect infinitive
A sequence consisting of to + have + past participle form of the verb. Examples are: I would like to have met Winston Churchill.