English Translation
He deceased yesterday.
The English is incorrect. “He died yesterday” would be correct.
He deceased yesterday.
The English is incorrect. “He died yesterday” would be correct.
Technically, decease is an English verb whose past tense is deceased, but it is only really used as a verb in legal documents in modern times.
I think the attempt in that translation is that fallecer is used as a “softer” alternative to morir, so He/she/it passed away yesterday might be a desirable alternative.
The use of “decease” as a verb is archaic. “Passed away” would indeed be preferable. I’ve been an editor of scholarly books for many years.