I read a title that made me wonder on SO because it used the third singular person where the plural one should have been used as I would in my native language.
Well, I thought it had been asked before, but I don’t see it at a quick glance. Note that this is not about grammar per se, but rather about grammatical-number.
If it is something you can look up in the dictionary, you should not ask, because it will be closed as Off-Topic.
There is no real way to predict the perfect stem or the supine stem (past-participle stem) of a Latin verb; there are only probabilities. One normally learns the past stems of a verb along with its present stem and conjugation group if they are irregular.
The regular suffix to form the perfect...
@Cerberus Done, but 1) three more to go, and 2) the close reason as given is correct (it's about one language). I don't agree with the close reason (I'm for keeping interesting questions open even if they're not exactly on-topic; follow stupid rules is too stupid. There's other crap to worry about.
The cited sentence is a perfectly idiomatic, natural, and common use of the past perfect construction in English. You will eventually grow accustomed to it and understand when its nuance is preferred. — tchrist15 mins ago
@tchrist; Still, I don't see how your comment is useful apart from showing your condescension... — jules2 mins ago