Sometimes the same exercise will give you definite and/or singular because it knows that on the English side it can be said several ways all with the same Swedish translation. It generates stuff randomly and there's at least six ways it can do this sentence because the English isn't picky.
"In the summer" is basically short for "in the summer time" or in other words "in times when it is summer" and so "in Summers" really means the exact same thing. To really refer to a singular summer in English, you'd have to say something like "this summer" or "that summer".
Native US English speaker - I don't believe "in the summers/falls/springs/winters" is appropriate, with the exception of the phrase "In all the summers" (for instance "In all the winters I spent at that cabin, never once did I see a bear"). Otherwise using a singular season name feels perfectly fine.
I would not say "I swim in all the summers".
In the U.S. we would say, ''I swim every summer'' but ''I swim most summers'' even ''the summers are hot where I live'' I'm just meaning that English is every bit as quirky as Swedish. My goal is to be able to communicate enough that a native Swedish speaker can understand my meaning most of the time...Understanding is difficult enough between native speakers of any language.
It is grammatical to say it with or without the plural. It's also grammatical to say it with or without making it definite. The meaning can be the same. The word summer can be a mass-noun but also can be countable. We melt in summer can mean the same thing as We melt in the summers. It doesn't mean it has to be every summer but that it seems to be recurring. If you wanted to say every summer, you would say every summer. There's no reason this exercise shouldn't accept more than one English phrase as a legitimate translation.
It's just not 1:1. In English, if you habitually swim during the season, you can easily say "in the summers" or "in summer" or a dozen other ways. They all mean the same thing. However, I think all of those English phrases translate into på somrarna in this course and you can translate that one Swedish phrase into whichever English version you prefer.
It's just that different prepositions are used for different time periods:
With seasons, we say på: på sommaren, på hösten, på vintern, på våren 'in summer, in autumn, in winter, in spring'
For months we use i: i januari 'in January' etc
For days of the week, we also use på: på måndag, på tisdag 'on Monday, on Tuesday' and so on.
Actually i sommar means 'this summer' so it would get a futural meaning and should be We will swim this summer in English.
It's just that we use different prepositions. In Swedish, the normal preposition for seasons is på, but in English you don't use on with seasons that way: you just don't say 'I swim on summer'.
Swedish doesn't distinguish between the simple present and the present continuous, so basically every Swedish sentence in the present can be either of those in English.
In many cases, the Swedish present tense can also express future. It certainly does that to a much larger extent than the English present. But for a translation in the future tense (with will or are going to) to be an accepted answer in this course, there has to be some support for that interpretation in the sentence. In this case, the most likely interpretation of this sentence with no context, is that it refers to something we do habitually.
I'm still not quite grasping word order. This follows the v2 rule because there's no object? Just a time phrase "in the summer"? If the sentence was "we swim in the lake in the summer" would it be "På somrana simmar vi sjön"? following verb subject object "vso"? All the while still following the v2 rule due to the time phrase "in the summer"?
what does på, i, and om mean????? I read on duo that på is for future/general and i is in the future but that didn't work so I looked on Swedish mad easy and it said om is future (om ett år - in a years time), I is for length of time (Jag har studerat svenska i 2 år - I have studied Swedish for 2 years), if its not happening for a length of time it's på (Jag har inte gått på gymmet på 2 veckor – I have not been to the gym for 2 weeks) also för ... sedan is past tense (för ett år sedan - a year ago). here's the page for anyone wondering https://swedishmadeeasy.com/time-prepositions-i-pa-and-om.html