Just to confirm: "Barn"= one child or many children "Barnet"=the child "Barna" or "barnene"=the children.
None, they are interchangeable. Several nouns can choose between -ene and -a in plural decisive form.
Because "barna" is the definite form, "the children".
"All children" = "alle barn"
I've was taught that sometimes a sentence with a word ending in 'r' followed by a word beginning with 's' often make a 'sh' sound (the example was 'vær så...'). Can it do that here too?
It's plural. The children. Snill is the singular masculine and feminine form, snilt for neuter (et barn, a child), and snille for plural.
I would say 'kind' and 'sweet' are fairly synonymous in English, but it doesn't accept 'sweet' as a meaning for 'snille'. Is sweet not used that way in Norwegian?
"all the cildren are polite" should be accepted because kind and polite are sinonims
Snill != høflig. Kind and polite might be synonymous, but the Norwegian word snill does not translate into "polite" (høflig).