The Forms of the Participles

a) The forms of Participle I are shown in the table below:

The Indefinite forms of Participle I express the action simultaneous with that of the main verb:

While completing the project we were very busy,

while the Perfect forms express the action prior to that of the main verb of the sentence:

The project having been completed, we all went on holiday.

b) Participle II has only one form – the 3d form of the verb: completed, thought, expressed, placed etc.:

The idea expressed in this film is not new.