Surely "trinkst" is second person singular, "Du trinkst". Third person singular is "trinkt".
Not a good metric. The second person plural, "ihr", does not take the "-en" ending. In this instance, the correct form is "ihr trinkt". The verb endings are not specifically about whether they are plural or not.
As for the noun endings, there are quite a few different possibilities for plurals. "-en" is only one. You really have to learn them separately.
Would this be for all plurals? Using the plural "sie" that is i.e. "sie = they"
German verbs change depending on the person or people they refer to. So, "You drink" is "Du trinkst", "We drink" is "Wir trinken", "He drinks is "Er drinkt", "The man drinks" is "Der Mann drinkt", and so on.
It's not die Junge, it's die Jungen (the boys) -- plural. Thus you need the third-person plural verb trinken.
der Junge trinkt would be "the boy drinks / the boy is drinking" -- the singular "the boy" is der Junge (Junge is grammatically masculine in German). And since it's singular, you need the third-person singular verb trinkt here.
Like the difference between "the boy is drinking" with "is" versus "the boys are drinking" with "are", depending on whether it's one boy or many.
I'm sure I remember that when I learned German in school, "boy" was "Knabe". Has that word gone out of use?
I expect you a right. Certainly "Knabe" is (or at least was) used for "boy" - Goethe's poem "Heidenröslein" begins: "Sah ein Knab' ein Röslein stehn, Röslein auf der Heiden", and the same poet's "Erlkönig" starts: "Wer reitet so spät durch Nacht und Wind? Es ist der Vater mit seinem Kind; Er hat den Knaben wohl in dem Arm, Er faßt ihn sicher, er hält ihn warm." I know those poems were written many years ago, but if "Knabe" was good enough for Goethe.......
Because it says, "Die Jungen" (the boys), and in English it would not be correct to say, "The boys drinks water".
It is the way verbs work in German. In English, verbs usually change very little. For example in the present tense of "to drink", we have: I drink, you (singular) drink, he drinks, she drinks, it drinks, we drink, you (plural) drink, they drink. But in German, the verb endings differ much more depending on the noun or pronoun the verb accompanies. That is why there are forms like "trinkt" and "trinken".
If you mean "When should I use "trinkt" and when should I rather use "trinken"? the answer is that "trinkt" is for third person singular (er, sie, es, or in English, he, she, it) and "trinken" is for plurals, like wir, Sie, Ihr (in English, we, you, they).
Sometimes, duolingo uses 'drink' and sometimes 'are drinking' as the translation for the same form trinken. That is confusing, I mean, we should now when to use Present Simple and Present Continuous.
Not quite sure what you mean. If you meant, "How do we know when to use "trinkst", when to use "trinkt, when to use "trinken", and so on, it's just part of learning German to learn that for instance, "du" has "trinkst", "wir" has "trinken" and so on.
It all depends on who is drinking. "I drink" is "Ich trinke", "You (singular) drink" is "du trinkst", "he (or she, or it, or the cat, or Simon, or....) drinks is "Er (or sie, or es, or die Katze, or Simon, or ...) trinkt", "We drink" is "wir trinken", "You (plural) drink" is "Sie trinken", and "They (or the cats, or Simon and Hans, or ....) drink" is "Sie (or die Katzen, or Simon und Hans, or ....) trinken".
Sorry - my fault entirely, and I knew that really. Apologies for the confusion!
Are you sure you put exactly the same as the correct answer, "Die Jungen trinken Wasser"? If you did, and it was marked wrong, report it.
Is this an exercise where you have a "word bank" at the bottom and have to tap the right words in the right order to make a sentence that translates Duo's sentence?
Which words do you have available?
I'm also confused by your use of the phrase "the wrong answer", implying that there is exactly one possible wrong answer.
Can you provide a screenshot, perhaps, please?
Yes, the so-called "present continuous" tense formed in English with "is/are ....ing" is the same as the simple present in German. However, why spend time typing out the extra letters? :)
In second person singular, you are directly talking to someone. So, if you want to say- you are drinking water : du trinkst Wasser. ( Emphasis on "st" at the ending of the verb, here, drinking)
For third person singular, you are talking about someone else with someone else. So, if you want to say- He is drinking water: er trinkt Wasser. ( Emphasis on the lack of a "st" ending, it is just a "t" ending at the end of the verb, here, drinking)
So to sum it up:
I drink: ich trinke .
You drink: du trinkst .
He drinks: er trinkt.
I was under the impression that any noun requires a definite/indefinite article in German.
Singular countable nouns almost always need a determiner before them (e.g. a definite or indefinite article).
Wasser is singular but uncountable.
So is "Die Jungen trinken das Wasser" incorrect?
No, but it means "the boys are drinking the water" (i.e. a particular quantity or source of water), rather than "the boys are drinking water" (in general).
So it's correct as a sentence, but incorrect as a translation of "the boys are drinking water".
The verb "trinken" (to drink) has a different form depending on who is doing the drinking. In English, we make only one distinction -
he/she/it drinks <<<
In many other languages, there are more distinctions:
ich trinke (I drink/am drinking)
du trinkst (you [informal singular] drink/are drinking)
er/sie/es trinkt (he/she/it drinks/is drinking)
wir trinken (we drink/are drinking)
ihr trinkt (you [informal plural] drink/are drinking)
sie/Sie trinken (they/you [formal, sing. or pl.] drink/are drinking)
For your future reference:
Later edit - added the English progressive versions to the translation. German doesn't have progressive tenses, so either translation can be correct, depending on English usage.