Past participle

Definition and stakes

George Abraham Grierson 1911 Encyclopædia Britannica (1911)

The strong past participle is more indefinite, and is employed to form a tense corresponding to the Greek aorist. The pluperfect participle refers to something which happened a long time ago, and is used to form the past tense of narration. As the third conjugation has no weak past participle, the strong past participle is employed to make the immediate past, and the pluperfect participle is employed to make the aorist past, while the new pluperfect participle is formed to make the tense of narration.
Source: Wikisource

Frank Edgar Farley An Advanced English Grammar with Exercises

Prove has past tense and past participle proved. The past participle proven should be avoided.
Work has past tense and past participle worked. Wrought in the past tense and the past participle is archaic, but is also modern as an adjective (as in wrought iron) .
Some verbs have rare or archaic weak forms alongside of the strong forms; thus digged, shined, past tense and past participle of dig, shine; showed, past participle of show.
Ate and eaten are preferred to eat (pronounced ĕt) .
Quoth, “said,” is an old strong past tense. The compound bequeath has bequeathed only.
Source: Gutenberg

Various Encyclopaedia Britannica, 11th Edition…

In the case of tenses formed from the past participle, the auxiliary is appended, not to the participle, but to the past tense, as in mī̃ uṭhalō̃ āhē, I have risen; myā mārilā āhē (personal passive construction) or myā mārilễ āhē (impersonal passive construction) , I have killed. Similarly mī uṭhalō̃ hōtō̃ (active construction) , I had risen. The usual forms of the present and past of the verb substantive are:—
The past changes for gender, but the present is immutable in this respect.
Source: Gutenberg

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