Learn Finnish: Kannella oli verta. - There was blood on the deck.

This is an existential sentence, which states that something exists in a particular place. In Finnish, these sentences usually start with the location (kannella), followed by the verb (oli), and end with the new information, the subject (verta). This structure is the Finnish equivalent of the English "There is/was..." construction.

Why is the word for blood in the partitive case (verta)?

Because blood is an uncountable mass noun. In Finnish existential sentences, if the thing existing is an uncountable substance (like water, air, or blood), it must be in the partitive case to indicate that there was "some" of it, rather than all the blood in the world.

What is the base form of kannella, and why does it change so much?

The nominative base form is kansi (deck or lid). In older Finnish words ending in -si, the stem often changes to -te- or -ne-. Here, consonant gradation weakens the ns to nn, creating the stem kanne-. We then add the adessive ending -lla (on) to get kannella.

How would the location case change if I used the verb jäädä (to remain) from this current lesson?