Learn Hardcore Finnish: Kirjoittaminen muistikirjaan auttaa minua muistamaan sanat. - Writing in a notebook helps me remember the words.

So grammatically it behaves like a noun (you can put it in cases: kirjoittamisen, kirjoittamisesta, etc.), but its meaning is still very close to the verb.

Why does muistikirjaan end in -an? How is that different from muistikirjassa or just muistikirja?

The ending -an in muistikirjaan marks the illative case, which usually means into something or to a place.

muistikirja = a notebook (basic form)
muistikirjaan = into a notebook
muistikirjassa = in a notebook (inside it)

So:

Kirjoittaminen muistikirjaan = writing into a notebook (you move the words into it)
Kirjoittaminen muistikirjassa would sound like writing in a notebook in the sense of doing some writing while you are in/inside a notebook – which is odd. You normally want into here.

That’s why -an (illative) is used.

How does Finnish express “into a notebook” without a preposition like “into”?

Finnish mostly uses case endings instead of prepositions.

In English:

into a notebook = preposition into
- noun notebook

In Finnish:

muistikirja
- -an → muistikirjaan = into a notebook

So the -an ending contains the meaning of into/to. There is usually no separate word like into or to in front of it; the ending does the job.

Why is it auttaa minua muistamaan, with two verb forms, and not something like auttaa minua muistaa?

After auttaa (to help), Finnish does not use the basic infinitive muistaa here. Instead, it uses the -maan / -mään form:

auttaa muistamaan = to help (someone) to remember

So:

auttaa minua muistamaan = helps me (to) remember

The pattern is:

auttaa + (object) + verb in -maan/-mään form

Using auttaa minua muistaa is ungrammatical in this meaning. The second verb must be in the -maan/-mään form, not in the basic infinitive.

What exact form is muistamaan, and when do I use this -maan / -mään form?

Muistamaan is the illative of the third infinitive (often called the -maan/-mään form).

Verb: muistaa (to remember)
3rd infinitive illative: muistamaan

This form is widely used:

After many verbs that express help, starting, going, coming, etc.:
- auttaa muistamaan = help to remember
- mennä nukkumaan = go to sleep
- alkaa lukemaan (esp. colloquial) = start reading
To express goal or purpose:
- Teen muistiinpanoja muistamaan asian paremmin.
  = I take notes (in order) to remember the matter better.

So in your sentence, muistamaan means roughly to remember / remembering (as a goal or result).

Why is it minua and not minut or minä?

Minua is the partitive form of minä (I).

The key point: auttaa normally takes its person object in the partitive:

Autatko minua? = Will you help me?
Hän auttaa sinua. = He/She helps you.

So:

auttaa minua muistamaan = helps me to remember

Compare:

minä = I (subject form)
minut = me (accusative, total object; used in special “endpoint” meanings)
minua = me (partitive; often the default with auttaa)

You can see minut with auttaa, but then there is a clear physical or endpoint result:

Hän auttoi minut ylös. = He helped me up.
Hän auttoi meidät maaliin. = He got us to the finish line.

In your sentence, there is no such physical endpoint; it’s general help, so minua is the normal choice.

Why is sanat used and not sanoja?

This is about the total object (nominative) vs partitive object.

sanat = “the words” as a total object (all of them)
sanoja = “(some) words” as a partitive object (some/indefinite amount)

Muistamaan sanat suggests a complete remembering of a definite set of words:

... auttaa minua muistamaan sanat.
≈ helps me remember the words (all of them).

If you said:

... auttaa minua muistamaan sanoja.

it would sound more like:

helps me remember (some) words / to remember words in general,
not necessarily a specific set that you want to remember fully.

So sanat fits the idea of remembering the vocabulary items you’re studying.

Can I change the word order, for example Muistikirjaan kirjoittaminen auttaa minua muistamaan sanat? Does it sound more natural?

Yes, you can, and many native speakers would probably prefer that order in writing:

Muistikirjaan kirjoittaminen auttaa minua muistamaan sanat.

Both versions are grammatical:

Kirjoittaminen muistikirjaan auttaa ...
Muistikirjaan kirjoittaminen auttaa ...

The difference is mostly emphasis:

Version 1 starts with the act of writing in general.
Version 2 starts by highlighting the place / target (into the notebook), then says that this kind of writing helps.

Neither is wrong; word order in Finnish is flexible and often used for nuance and emphasis rather than strict grammar.

Could I use kirjoitus instead of kirjoittaminen, like Kirjoitus muistikirjaan auttaa minua muistamaan sanat?

Not really, at least not with the same meaning.

kirjoittaminen = the activity of writing, the act itself
kirjoitus = a piece of writing, a text, an essay, an article, etc.

So:

Kirjoittaminen muistikirjaan auttaa ...
= The act of writing into a notebook helps ...
Kirjoitus muistikirjaan auttaa ...
sounds like A (specific) text written into a notebook helps ..., which is strange in this context.

To talk about the habit or method of writing as a learning strategy, kirjoittaminen is the correct word.

How would I say “Writing in my notebook helps me remember the words”?

You need to add possession (my) to muistikirja.

One direct version matching the structure of your sentence:

Muistikirjaani kirjoittaminen auttaa minua muistamaan sanat.

Here:

muistikirja = notebook
muistikirjaani = into my notebook
- muistikirja
  - illative -an
    - possessive -ni → muistikirjaani

A more everyday version with a finite verb:

Kun kirjoitan sanat muistikirjaani, se auttaa minua muistamaan ne.
= When I write the words in my notebook, it helps me remember them.

How could I say the same idea using a full clause with että instead of kirjoittaminen?

You can replace the verbal noun kirjoittaminen with a clause introduced by että (that):

Se, että kirjoitan sanat muistikirjaan, auttaa minua muistamaan ne.
= The fact that I write the words in a notebook helps me remember them.

Breakdown:

Se, että ... = The fact that ...
kirjoitan sanat muistikirjaan = I write the words into a notebook
auttaa minua muistamaan ne = helps me remember them

This is often a bit more conversational than the abstract verbal noun, and it’s a very common structure in Finnish.

How do I know whether muistikirjaan means “into a notebook” or “into the notebook”, since Finnish has no articles?

Finnish simply does not mark the difference between a notebook and the notebook in the noun form itself.

muistikirjaan can mean:
- into a notebook
- into the notebook

Which one is correct in English depends on context:

If you’re talking about your general learning habit, English might prefer “in a notebook”.
If you already mentioned a specific notebook (e.g., my vocabulary notebook), English might use “in the notebook”.

Finnish leaves this unspecified; muistikirjaan covers both.

Why is auttaa in the 3rd person singular (auttaa) and not plural (auttavat), even though sanat (words) is plural?

The subject of the sentence is Kirjoittaminen muistikirjaan, which is singular (a single activity):

Kirjoittaminen muistikirjaan = Writing in a notebook
auttaa = helps (3rd person singular)
minua muistamaan sanat = me remember the words

The plural noun sanat is the object of muistamaan, not the subject of auttaa. Subject–verb agreement in Finnish works with the grammatical subject, which here is the singular verbal noun kirjoittaminen.