Learn Hardcore Finnish: Minä menen takaisin kotiin.

It’s not grammatically required. If you leave it out, the sentence still means that you’re going home, but without emphasizing the idea of returning.

Why is it menen and not something like mennän?

The dictionary (infinitive) form is mennä = to go.

In Finnish, verbs are conjugated, and mennä has a stem mene- in the present tense. For the 1st person singular:

stem: mene-
personal ending: -n

→ mene + n = menen = I go / I am going

So the present tense forms are:

minä menen = I go
sinä menet = you go
hän menee = he/she goes
me menemme = we go
te menette = you (pl.) go
he menevät = they go

The double nn appears in mennä (the infinitive), but not in the present stem.

Do I have to say Minä, or can I just say Menen takaisin kotiin?

You can absolutely drop Minä:

Menen takaisin kotiin.

This is completely natural Finnish. The verb ending -n in menen already tells us the subject is I, so the pronoun is not needed.

Use Minä menen takaisin kotiin when you want to emphasize I as the subject, for example:

Minä menen takaisin kotiin, en sinä.
I am going back home, not you.

Why is it kotiin and not koteen? The ending looks different from other words.

Finnish has several patterns for forming the illative (the “into/to” case).
For many words, you see endings like -seen, -Vn, or -hin, but koti is in a group where -in is added:

koti → kotiin (home → to home)
vesi → veteen (water → into water)
talo → taloon (house → into the house)

So you can’t just mechanically add -een; you have to learn the pattern for each word type. For koti, the correct illative is kotiin.

What case is kotiin, and what are the other forms like “at home” and “from home”?

kotiin is the illative case (movement into / to a place).

Common forms of koti:

koti (nominative) – home (basic dictionary form)
kotona (inessive) – at home
kotoa (elative) – from home
kotiin (illative) – to home

Examples:

Olen kotona. = I am at home.
Lähden kotoa. = I leave from home.
Menen kotiin. = I go home.

Can I change the word order, like Minä menen kotiin takaisin?

You can say Minä menen kotiin takaisin, and people will understand you. It is grammatically possible, but it sounds less natural as a neutral sentence.

The most natural, neutral orders are:

Menen takaisin kotiin.
Menen kotiin takaisin. (acceptable, but a bit less common)

Finnish word order is somewhat flexible, but adverbs like takaisin often come before the destination phrase. Minä menen takaisin kotiin is the most typical and natural version.

How do I say this in the past or future?

The sentence you gave is in the present tense:

Minä menen takaisin kotiin. = I go / I am going back home.

For the past tense (simple past), use the imperfect:

Minä menin takaisin kotiin. = I went back home.

For future meaning, Finnish usually still uses the present tense and relies on context or time expressions:

Huomenna menen takaisin kotiin. = Tomorrow I will go back home.
Kohta menen takaisin kotiin. = I will go back home soon.

So there is no separate future tense form of the verb.

What is the difference between mennä and tulla, and could I use tulla here?

mennä = to go (movement away from the speaker’s current position)
tulla = to come (movement towards the speaker or some reference point)

Minä menen takaisin kotiin. describes you going back home, from wherever you are now.

You could use tulla in a sentence like:

Minä tulen takaisin kotiin. = I am coming back home.

This is more about arriving to home (often from the perspective of someone who is at home or thinking about home as the destination). Context decides which feels more natural, but both are grammatically fine.

How does Finnish say “I’m going back home” vs “I go back home”? Is there a difference?

Finnish present tense covers both English simple present and present continuous:

Minä menen takaisin kotiin.
= I go back home.
= I am going back home.

The verb form menen does not change; only the English translation does. Context (time expressions, situation) will clarify whether it’s a one‑time action happening now, a plan, or a habitual action.

How do I say my home, your home, etc., in this sentence?

In Finnish, you often use possessive suffixes instead of (or in addition to) separate pronouns. With kotiin:

kotiin = to (a/the) home
kotiini = to my home
kotiisi = to your (sg.) home
kotiinsa = to his/her/their home

So you could say:

Menen takaisin kotiini. = I am going back to my home.
Menen takaisin kotiisi. = I am going back to your home.

In many contexts, kotiin already implies “(my) home” if you’re talking about yourself, so kotiin alone is often enough.

Is there another verb I could use instead of mennä to say “go back home”?

Yes. A very common alternative is palata = to return, to come back.

Minä palaan kotiin. = I return home / I come back home.
Minä palaan takaisin kotiin. = I return back home (a bit redundant in English, but fine in Finnish).

Minä menen takaisin kotiin focuses more on the movement of going.
Minä palaan kotiin focuses more on the idea of returning.