It really isn’t a modern Swedish letter.
My Swedish-English dictionary only lists a single word under Q, Quisling, which was the last name of the Norwegian who ruled his country on behalf of the Nazi occupiers during World War Two. It has become the brand name for a collaborator or traitor.
But it’s Norwegian, not Swedish. (Or French)
Otherwise, the most common q words you might see here are quiche or Qatar, foreign words with no Swedish counterpart, so they’ve just been more or less dropped in to Swedish as they are.
Where English uses q, modern Swedish has k, and the English q-u is k-v in Swedish, as in kväll the word for evening, and i-kväll, which means tonight.
This isn’t the only place where we’re going to have trouble doing this abc…there are almost no Swedish words that start with the letter X, and the English letters V and W are basically interchangeable in Swedish, to the point of being listed all mixed up together in the telephone book.
On the other hand, Swedish has three letters you don’t find in English, the a with a circle over it, and the a and e with two dots over them.
We’ll get to those in the fullness of time…
Anyway, back to q. You do see q-v instead of k-v sometimes to give kind of an old-fashioned feeling to a word. My favorite is kvarn, the word for mill. If you spell it with a q instead of the k, it’s sort of like saying ye olde shoppe in English. Trendy old-fashionness…