Pakkaan vettä retkeä varten.

Pakkaan is the 1st person singular present form of pakata, which means to pack.

So:

• pakata = to pack
• pakkaan = I pack / I am packing

In Finnish, the ending -n shows that the subject is I.

Because Finnish usually does not need a subject pronoun when the verb ending already shows the person.

• pakkaan already means I pack / I’m packing
• so minä is usually left out

You could say Minä pakkaan vettä retkeä varten, but that sounds more emphatic, like I’m the one packing water for the trip.

Vettä is the partitive singular of vesi.

Finnish often uses the partitive for:

• an unspecified amount
• a mass noun or substance
• something that is not being treated as a complete whole

So pakkaan vettä means something like I’m packing some water.

By contrast:

• vesi is the basic dictionary form
• veden would suggest a more specific, bounded amount, which is less natural here unless the context makes that very clear

Yes, vesi is one of those nouns whose stem changes when it is inflected.

Important forms to learn are:

• vesi = water
• veden = of the water / the water
• vettä = water (partitive)

So this is not just vesi + ending. The word changes shape as well. That is normal in Finnish, and vesi is a very common word, so it is worth memorizing as a small pattern of its own.

Because varten requires the partitive case.

So:

• retki = trip, excursion
• retkeä = trip in the partitive singular

That means retkeä varten literally has the structure for a/the trip, with retkeä in the case that varten demands.

Varten means for, especially in the sense of:

• for the purpose of
• intended for
• in preparation for

So retkeä varten means for the trip or for the purpose of the trip.

It often sounds a little more purposeful than a simple English for.

Because varten is a postposition, not a preposition.

In English, we say:

• for the trip

In Finnish, the matching word comes after the noun phrase:

• retkeä varten

So the pattern is:

• noun in the required case + varten

Grammatically, it is present tense, but Finnish present tense can also cover meanings that English might express with the future.

So Pakkaan vettä retkeä varten can mean:

• I’m packing water for the trip
• I pack water for the trip
• sometimes, depending on context, I’ll pack water for the trip

Usually the surrounding context tells you which English translation is best.

The word order here is the most neutral one:

• Pakkaan = verb
• vettä = object
• retkeä varten = purpose phrase

But Finnish word order is fairly flexible. You can move parts around for emphasis.

For example:

• Retkeä varten pakkaan vettä.

This still means the same basic thing, but now for the trip is more strongly highlighted.