Learn Icelandic: Við ætlum að sleppa formálanum og innganginum. - We are going to skip the preface and the introduction.

The verb sleppa governs the dative case when it means "to skip," "to omit," or "to let go of" something. Because we are actively skipping the preface and introduction, both objects must take the dative.

Doesn't sleppa usually mean "to escape"?

Sleppa has two closely related meanings depending on how it is used. When it takes a dative object, like in this sentence, it means "to let something go" or "to skip something." When it is used without an object (intransitive), it means "to escape" or "to get away," as in við sluppum (we escaped).

How do the dictionary forms of these nouns change to become formálanum and innganginum?

The dictionary forms are the masculine nouns formáli and inngangur. In the dative singular, they become formála and inngangi. To say "the" preface and "the" introduction, we attach the dative masculine definite article -num, giving us formálanum and innganginum.

Could we just use the present tense við sleppum to mean "we will skip"?

Yes, the present tense in Icelandic is frequently used to express future actions. However, using ætla að (to intend to) plus the infinitive sleppa specifically emphasizes a deliberate plan or intention, perfectly matching the English "we are going to skip."