Konnten vs. könnten
I thought I knew the difference, but maybe not. How can they mean the same thing in the same context, but still be different? Or is Duo just flipping out on me again?
The problem is that the word "could" in English has two different meanings:
"When I was younger, I could ride a bike" -- past tense of "can". "Als ich klein war, konnte ich Rad fahren."
"If I am lucky, I could become president" -- subjunctive. "Wenn ich Glück habe, könnte ich Präsident werden."
It is important to distinguish between the two kinds of "could" in English to understand the difference between konnten and könnten in German.
Keep in mind that "konnten" is an actual tense (past/pretäritum) from the verb "können", whereas "könnten" is merely a mood from that same verb. Think of "könnten" as the wishy-washy brother of "konnten".
I think a lot of German learners overcomplicate things in this particular topic because they forget that the conditional or subjunctive form of a word is a mood and not a tense at all.
Maybe one way to help is to think of "konnten" as "could" and "könnten" as "might" . Feel the difference there? Ich konnte das tun, weil.... I could do that, because...
Ich könnte das tun, wenn... I might do that, if...
This is the same with "mochten" versus "möchten". Er mochte seinen Kaffee. He liked his coffee. That is a plain, blunt statement. Something happened in the past, and we are recalling it. Er möchte einen Kaffee. He would like a coffee. Or, perhaps better, "He fancies a coffee". Using "fancy" as a verb is a British thing, but I love it and I think it somehow works in this context. He fancies it, although he doesn't yet have it. The thing has not happened, but if he asks politely enough or finds a café it just might! Think of the conditional mood as currency used in a kind of Limbo Land.
And, of course, we can add more complexity: If I (in the past) had wanted a coffee, (then) I would have asked for one. Wenn ich einen Kaffee gewollt hätte, dann hätte ich nach einen gefragt.
Notice how that wishy-washy sentiment is set in the past, but the conditional form of the verb remains in Limbo-land: hätte and not hatte.
It is the same with konnten and könnten.
But notice what happens when you introduce a modal verb such as können with conditional phrase set in the past: I might have ordered a coffee, if I had had more time.
Ich hätte einen Kaffee bestellen können, wenn ich mehr Zeit hätte.
This was the trickiest part for me, namely combining "hätte" with "können". When you use any model verb in the past in the conditional mood, you always use a form of "hätten" along with a double-infinitive ending, with the conditional verb (in all its infinitive glory) kicked to the very end.
Oh, the joys of learning the German language!!!
Hope that helps!
Sie könnten lesen... (They could read) = subjunctive , like the miss said, they have the possibility.
Sie könnten lesen, wenn sie ihre Brillen hätten. ~ subjunctive
Sie konnten lesen, (zur Zeit) als sie ihre Brillen hatten. ~ They could read to the time they had their glasses.
I always thought "konnten" meant "could have" as opposed to "could." While the sentence in your second example is used commonly in English, it's technically mixing tenses and grammatically incorrect. The correct way to say it would be, "They could have read when (at the time) they had their glasses." The commonly used mixed tense "could" would translate to "könnten," not "konnten."
"It rained yesterday so I couldn't hang up my clothing."
You mean you would have to say that as "It rained yesterday so I couldn't have hung up my clothing" in order not to "mix tenses and be grammatically incorrect"?
What about "When I was a child, we went to Italy on vacation every year. The sun always shines there and so we could swim there every year.".
Do you say that as "...and so we could have swum there every year"?
First time I hear about a variety of English without a simple past form of "can".
"Could have" (and also "should have") actually take a completely different approach in German; you can't think directly from the English when constructing this idea in German.
I could have done = Ich hätte machen können. So the verb that could have been done, takes the infinitive (unlike the past participle in English). The literal English translation of this German construction is "I would have been able to do."
So - I could have read the book = Ich hätte das Buch lesen können.
The German idea is actually identical to both the French and Italian: "J'aurais dû faire" / "Avrei dovuto fare" (Literally "I would have been able to do").
Similarly, I should have done = Ich hätte machen sollen. Literally translated, it's utter nonsense in English: "I would have should do".