"The girls and the boys"
Translation:Flickorna och pojkarna
Here are some general rules for forming plurals in Swedish: If it is an en-word and ends in -a, you add -or (example: kvinna to kvinnor). If it is an en-word and has one syllable or ends in an unstressed syllable, you add ar (example: hund to hundar). That group contains basically all of the en-words that don't end in -a. For some words in this group that end in unstressed syllables, you eliminate the vowel (example: fågel to fåglar). This may seem difficult, but you'll find it natural after a while. If it is an en-word and is a loanword from another language, add -er (example: biljett to biljetter). You also add -er for the "umlaut plurals," which add an umlaut in the plural form (example: fot to fötter). If it is an ett-word, it is the same in the plural, unless it ends in a vowel, in which case you add -n (example: äpple to "äpplen). This all may seem intimidating, but it'll be easy to remember after a while. The -na makes it definite (the). So a long answer for your short question: pojke is an en-word that doesn't end in -a, so you add -ar. Then, you add -na* to make it definite (the boys). Hope my lengthy explanation made sense!
I'm Swedish myself and never knew any of this. I haven't thought about the rules behind the grammar, I just kind of... learned it all. The rules are so complicated and there are so many exceptions for everything, it must be such a pain to learn Swedish as a second language. I'm really glad I got to learn it as my native language so that I don't have to perceive it as difficult.
Ok ok there is a serious problem here, I typed "Flickorna och pojkenar" and got it wrong because the "e" was supposed to be an "a", so I then typed "Flickorna och pojkanar" because that is what it said was correct, then it said I got it wrong and that "Flickorna och killarna" was correct or whatever the "k" word for boys is. Why did it not say Killarna the first time? Why did it say Pojkanar and then change to Killarna? Anyone know?
Pojke/kille are both accepted. There must have been some other mistake before when you were using pojke. For example you wrote "pojkanar" twice here?
As for suggesting "killarna" instead, sometimes Duolingo does that when you're making a mistake. It corrects you using different wording than what you were using.
They are technically synonyms, but it's more common to use flicka for a younger girl (approximately single-digit-age) and tjej for an older girl. Although some people use tjej for younger girls as well, especially to make them feel a little more grown up. I'd say flicka and pojke are less common in modern speech than tjej and kille, except when referring to young children. When you tell someone the sex of your newborn baby you'd probably use flicka or pojke. They're practically interchangable though - however, like Arnauti said, the combinations are flicka/pojke and tjej/kille, it sounds really weird if you say "flicka och kille" or "tjej och pojke".
This is all based on my experience as a native speaker.