Learn Hardcore Finnish: Odotan vartin ja sitten menen kotiin. - I will wait for a quarter of an hour and then I will go home.

Odotan = I wait / I’m waiting (1st person singular)
menen = I go / I’m going (1st person singular)
You can add minä for emphasis or contrast: Minä odotan vartin… (implying I will wait, maybe others won’t).

What does the -n in odotan mean?

In odotan, the ending -n marks 1st person singular in the present tense. The dictionary form is odottaa (to wait).
Conjugation pattern here:

minä odotan = I wait
sinä odotat = you wait
hän odottaa = he/she waits

What is vartin—and why is it not varttia?

Vartti means a quarter of an hour (15 minutes).
Both forms can occur, but they feel different:

Odotan vartin.
Uses the genitive/“accusative-like” form vartin to express a bounded, complete amount of time: I’ll wait (for) 15 minutes (and then stop).
Odotan varttia.
Uses the partitive varttia, which often feels more like I’ll wait for 15 minutes / I’ll be waiting for 15 minutes with a slightly more “ongoing” feel (and in some contexts can sound less “neatly bounded”).

In everyday Finnish, odottaa commonly takes the partitive for objects (odotan bussia = I’m waiting for the bus), but time expressions like this often allow the bounded -n form when the duration is seen as a complete unit.

Is vartti formal Finnish?

Vartti is very common and neutral in spoken and informal written Finnish. It’s essentially the everyday word for 15 minutes. In more formal contexts you might also see:

viisitoista minuuttia = fifteen minutes
But vartti is not “slangy” in a problematic way—just more conversational.

What case is kotiin, and what does it add?

Kotiin is the illative form of koti and means into/to (one’s) home—it expresses direction toward the inside of a place.

Compare:

kotiin = to home (toward/into home)
kotona = at home (location)
kodista = from home (out of home)

So menen kotiin specifically encodes going home (to the home) rather than just being home.

Why is it kotiin (double i) instead of something like kotin?

That’s how Finnish forms the illative for many words: it often lengthens a vowel and/or adds -n. For koti, the illative is kotiin. The long vowel is meaningful in Finnish spelling and pronunciation.

Does menen mean “I go” or “I will go” here?

Grammatically, menen is present tense (I go / I’m going), but Finnish often uses the present to talk about near-future plans, especially with context words like sitten (then). So in natural English it often corresponds to I’ll go.

What does sitten do in the sentence, and where can it go?

Sitten means then and marks the next step in a sequence.
The structure … ja sitten … is very common: it clearly signals first X, and then Y.

You can move it for emphasis, but the most natural is exactly what you have:

Odotan vartin ja sitten menen kotiin.

Alternatives are possible, with slight changes in rhythm/emphasis:

Odotan vartin, sitten menen kotiin. (still very natural)
Sitten menen kotiin. (as a standalone next-step sentence)

Why is ja used—could you just omit it?

ja means and and connects two actions into one smooth plan: I’ll wait 15 minutes and then I’ll go home.
You can omit ja and use punctuation instead, especially in writing:

Odotan vartin, sitten menen kotiin.
Both are correct; ja sitten just feels especially “flowing” and conversational.

Is the word order fixed, or can it be changed?

Finnish word order is fairly flexible, but changes often affect emphasis.

Neutral, natural:

Odotan vartin ja sitten menen kotiin.

If you front kotiin, it emphasizes home as the destination:

Kotiin menen sitten vartin odotettuani. (more literary/structured)

If you front the time, it emphasizes the waiting duration:

Vartin odotan ja sitten menen kotiin. (a bit marked, but possible)

The original sentence is the most straightforward everyday version.