"Estas bona lakto."
Translation:It is good milk.
Because that would usually be said as "Lakto estas bona" in Esperanto.
That's true. Maybe I should be more specific. I am confused about why gxi wasn't used. Shouldn't the translation of "It is good milk." be "Gxi estas bona lakto." ?
I would think that as well. Every sentence I've seen like this has led me to believe this means "There is some good milk", and that disembodied "estas" acts like the french "il y a".
Eh? I'm not sure where you got that idea.
In general, Esperanto is not pro-drop, but it doesn't usually do "dummy subjects".
So you have "pluvas" because there is no object that is raining, and "estas multaj bestoj tie" because you don't need the "there" that English has in "there are..." sentences.
But you wouldn't usually say "estas de mia patro" when talking about a book, I think, but "ĝi estas de mia patro".
-n is the accusative ending and is used mostly for direct objects.
"esti" doesn't have a direct object, though, but joins a subject with a predicate, which are both in the nominative case, without -n.