Learn Finnish: Iso keko on metsässä. - The large mound is in the forest.

Because Finnish doesn't have articles like "a" or "the", word order does that job. When the subject (iso keko) comes first, it usually refers to something specific and known, so it translates as "The large mound". If we wanted to say "There is a large mound in the forest", we would use the existential word order and start with the location: Metsässä on iso keko.

What kind of mound does keko usually refer to in a forest?

Keko means a pile, heap, or mound. In the context of a Finnish forest, it almost always refers to an anthill (muurahaiskeko). Wood ants build very large, distinctive pine needle mounds that are a common sight in Finland.

Since a mound is a collection of many things, why does it take a singular verb (on)?

Even though a keko consists of many small parts, the word itself is a single grammatical noun in the nominative case, so it takes the regular third-person singular verb (on). As you'll see in this lesson, when you use actual quantity words to describe multiple things (like paljon muurahaisia, "a lot of ants"), the verb stays singular, but the noun changes to the partitive case!

What would happen to iso if the sentence was "The ant is in the large mound"?