"Their mother is good."
Translation:Ilia patrino estas bona.
I would say estas bona is more common, but bonas is on the rise, especially among younger people.
Why is "panjo" not accepted? I know it translates more closely to "mom", but I've used it for other questions with the word mother, so why not this one?
bona is an adjective and bone is a adverb. every word ending in a is an adjective (describing a noun) every word ending in e is an adverb (describing a verb) every word ending in o is a noun no matter if feminine or masculine there are no grammatical genders. it is a kinda unnatural but when you get used to it, it gets easier
"Estas" is like an equal sign: lia patrino = bona. Nobody is doing anything to anything, so no need for the accusative suffix.