Learn Croatian: Nemamo sladak kolač. - We do not have a sweet cake.

The verb nemati (to not have) takes a direct object in the accusative case. However, for masculine inanimate nouns (objects that are not alive, like a cake), the accusative form is exactly the same as the basic nominative (dictionary) form. That is why kolač doesn't change.

Why doesn't the adjective sladak (sweet) get a new ending to match the accusative case?

Adjectives always copy the gender, number, and case of the noun they describe. Because kolač is a masculine inanimate noun in the accusative case, the adjective also uses the masculine inanimate accusative form. Just like the noun, this specific form looks identical to the basic dictionary form, so no extra endings are added.

Why is nemamo written as a single word? Shouldn't it be ne imamo?

Usually, the negative word ne is written separately in front of verbs (for example, ne radimo for "we don't work"). But the verb imati (to have) is a special exception. When negated, the ne merges with the verb and the letter "i" is dropped, creating a single word: nemam, nemaš, nemamo, etc.

If the adjective is sladak, why do I sometimes see it spelled as slatka?