In Swedish, there are three main conjunctions: och, eller, and men – “and”, “or”, and “but”, respectively. Conjunctions are grammatical words which are used to represent a connection between two words of the same kind. For example, en mor och en far – “a mother and a father”; glad men trött – “happy but tired”. Conjunctions are also used to join main clauses:

Jag ringde Kalle men han var inte hemma. – I called Kalle but he wasn’t home.
Ska du laga maten eller vill du hellre diska? – Are you going to cook the food, or would you rather do the dishes?

Not only can conjunctions be used to join main clauses to each other; they can also be used to join together subclauses:

[Hon tror] att han är sjuk eller att han sovit dåligt. – [She believes] that he’s sick or that he slept badly.
[De undrar] när han kommer och om han kan hämta hunden. – [They are wondering] when he’s coming and if he can fetch the dog.

Conjunctions show a certain relationship between words or phrases of the same type.

Subjunctions, on the other hand, are used to connect main clauses and subclauses. Examples of subclauses are att, när, om, där, vad, var, and various others, when they are used in this way.

What does that mean, though? Let’s take a look at the previous two examples:

[Hon tror] att han är sjuk, eller att han sovit dåligt. – [She believes] that he’s sick, or that he slept badly.
[De undrar] när han kommer, och om han kan hämta hunden. – [They are wondering] when he’s coming, and if he can fetch the dog.

(Here, the main clause is placed in [brackets], and the subjunction is underlined.)

You can see that the subjunction is what joins the main clause with the subclause:

hon tror att han är sjuk – she believes that he is sick

att han är sjuk “that he is sick” is a subclause because it is a component of a larger sentence (a “main clause”). That main sentence is hon tror ___ “she believes ___”. What does she believe? She believes that he is sick.

If we instead put och “and” where att “that” is, we would get hon tror och han är sjuk “she believes, and he is sick”. Now, han är sjuk “he is sick” is a separate thought which, while connected to hon tror “she believes”, is not a part within it. What does she believe? I don’t know, but he is sick. When och is used, we get two main clauses instead of a main clause and a subclause.

To reinforce, conjunctions connect main clauses with other main clauses, or subclauses with other subclauses. Subjunctions, on the other hand, connect main clauses with subclauses.

This difference is important because the two are used very differently. For some reason, in English, they are often placed in the same category, “conjunctions”. Swedish makes a clear distinction between conjunctions and subjunctions for logical reasons, and this makes it easier to describe grammar even in other areas of the language.