Learn Finnish: Ruoan säilytys on turvallista ilmatiiviissä rasiassa. - Food storage is safe in an airtight container.

In Finnish, when the subject of a sentence is an abstract concept, a process, or an uncountable mass noun, the predicative adjective (the adjective describing it after the verb 'to be') takes the partitive case. Because säilytys (storage) is an ongoing process rather than a concrete countable object, we use turvallista instead of turvallinen.

What is the base form of ilmatiiviissä, and how does its stem change here?

The base form is ilmatiivis (airtight), built from ilma (air) and tiivis (tight or dense). For adjectives ending in -is (like tiivis or valmis), the stem changes to -ii- before adding a case ending. We add the inessive ending -ssä ('in') to agree with rasiassa, giving us ilmatiiviissä.

How is the noun säilytys related to the verb for 'to store'?

It is derived directly from the verb säilyttää (to preserve, store, keep). In Finnish, using the stem of the verb and adding -s (giving the noun stem säilyty-) is a common way to turn an action into a noun, similar to adding '-tion' or '-ing' in English.

Since our current lesson is about niin kauan kuin (as long as), how could we rephrase this sentence to say 'Food storage is safe as long as it is in an airtight container'?