Learn Finnish: Tontut ostavat leipää keijuilta. - The elves buy bread from the fairies.

Start with the base word keiju (fairy). Add the plural marker -i- to get the plural stem keijui-. Then, add the ablative ending -lta (from), resulting in keijuilta (from the fairies).

Why do we use the ablative case (-lta/-ltä) for buying from someone?

In Finnish, when you get, buy, or ask for something from a person or a living being, you use the ablative case (-lta/-ltä). Think of it as receiving the item from their hands (an outer surface), rather than from inside them.

Why is leipää in the partitive case?

Leipä (bread) is an uncountable mass noun here. The partitive form leipää indicates that they are buying an unspecified amount (some bread), rather than one specific, whole loaf.

What is the base form of tontut and why does it end in -t?

The base form is tonttu (elf or gnome). The -t at the end makes it plural (tontut). Because the elves are the ones doing the action (the subject), they are in this basic nominative plural form.