When you want to say THEY the languages (are difficult), use nomin. pl. linguae. When you want to say THEM the languages (students study them), use accus. pl. linguās.
UPDATE: I should say, "THEM the languages is accus. pl. linguās when the verb is discunt; but THEM the languages is dative pl. linguīs, when the verb is student."
2nd update: If we have linguae in the sentence with discipulī student , then of course, linguae is dative singular, representing an "IT": The students are studying IT (the language).
I read that "studere" has to be used as an intransitive in proper Latin grammar: https://fr.wiktionary.org/wiki/studeo
So, I guess we must use "discunt" (verb discere) to say "They study English" for instance, in Latin.
False: -Studere latinam-
Right: Discere latinam
Linguam latinam discere
So, it doesn't take the direct object (accusative), but we can add a complement if we make it dative.
Dative: Linguis studere.
(Ego) amo studere linguis.
Well, the word disciple is something more akin to apprentice or follower. The disciples of the new testament were students of Jesus, who they often called teacher. While the words are indeed cognates, I would say that the best translation in the context that Duolingo gives is student, rather than disciple. If it was talking about a blacksmith or electrician, my preferred translation would be apprentice. If it were talking about a religious figure, then it would be disciple.
I'm new in Latin. I hope somebody can explain what this sentence "discipuli linguas discunt" really meant. This sentence translated as "the students learn languages".
My question is: Are the students really learn "many languages"? Or are they all learn one language?
"Linguas" is plural, so the students are learning more than one language.
Intro to Latin:
Here is a plain-English overview of what the cases are and how they work:
Latin cases, in English
Adjectives must agree in gender, number, and case with the nouns they modify, but they have their own declensions. Sometimes you get lucky and the adjective just happens to follow the same declension as the noun, but that is not a guarantee.