In Swedish, you show definite (the) by an ending, right? So ”the girl” = ”flickan”; we have no need for an English ”the” word. However, when we combine it with an adjective, we have to not only show that it’s definite in the noun or the adjective, we also need an article similar to English ”the”. So:
- En liten flicka = A little girl.
We put ”flicka” in the definite: ”flickan”. Then we put ”liten” in the definite, which is irregular, so it’s ”lilla”, and then we need an article similar to English ”the” as well. So you need to show it in three places!
- Den lilla flickan
Yes indeed, it's a conspicuous grammatical difference from Danish (but not from Norwegian)! There are remnants in southern Swedish from the Danish times, e.g "Stora Torg" for "The Main Square" where Standard Swedish would have "Stora Torget or Stortorget" (we usually exclude the definite "det" when it comes to names, in Swedish as well as in Danish)
Regarding this difference, we would not need a sentence. Translated into Danish, this phrase would be "den lille pige." Without the adjective, "flickan" in Swedish is "pigen" in Danish. The Danes either make the noun definite or, with an intervening adjective, use a definite article, but they do not do both at the same time. As JonAbelli points out, while Norwegian is often more like Danish than Swedish, it does the same as Swedish in this case.
The -e ending is strictly masculine. It's a remnant from when Swedish still made that grammatical difference, but today can only be used for actual masculinities. Thus, you might perhaps adress me as "käre moderator" to say "dear moderator".
The -a ending can be used for anyone, though, and is by far the most common. I recommend sticking to it if at all unsure.