Minä juon vettä siksi että se on terveellistä.

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Breakdown of Minä juon vettä siksi että se on terveellistä.

• olla: to be
• vesi: the water
• juoda: to drink

Questions & Answers about Minä juon vettä siksi että se on terveellistä.

Why is vettä used here instead of vesi or veden?

Vettä is the partitive case of vesi (water). Finnish uses the partitive object in several situations, and one of the most common is:

• when you are talking about an indefinite amount of something, especially a substance (water, coffee, milk, etc.)

So:

• Minä juon vettä. = I drink (some) water / I am drinking water.
  → an unspecified, not-all amount of water.

If you said:

• Minä juon veden.
  you would mean I drink the water (all of it) – a specific, delimited amount, like one glass/bottle that you finish completely.

Plain vesi (nominative) as an object (Minä juon vesi) would be ungrammatical.

So vettä is used because you are talking about water in general / some water, not “the whole water of some specific container”.

Why does terveellistä end in -stä? Why not terveellinen?

The base form is the adjective terveellinen (healthy, healthful).
In the sentence, we have:

• se on terveellistä

Here terveellistä is in the partitive singular. There are two main ideas to know:

1. After olla (to be), the “description word” (predicative) can be nominative or partitive in Finnish.
2. When you talk about a substance or a general property, Finnish often uses the .