Learn Hardcore Finnish: Puolisoni kirjoitti minulle rohkaisevan viestin, jossa hän sanoi, että pienet virheet kuuluvat oppimiseen. - My spouse wrote me an encouraging message in which she/he said that small mistakes are a part of learning.

Using both (minun puolisoni) is possible and common in speech; it adds emphasis, a bit like saying my own spouse. In neutral written Finnish, puolisoni alone is often enough.

Finnish doesn’t use separate articles like a/the, so there’s no extra word for a or the here either.

Why is minulle used, and what case is it?

Minulle is the allative case of minä (I).

minä = I
minulle = to me (allative)

With verbs of giving or sending something to someone, Finnish normally uses the allative:

kirjoittaa jollekin = to write to someone
- Puolisoni kirjoitti minulle = My spouse wrote to me
antaa minulle = give to me
lähettää minulle = send to me

You would not say kirjoitti minua here; minua (partitive) would mean something like wrote me as the direct object, which is wrong in this context. The person is a recipient, not the thing being written.

Why is it rohkaisevan viestin instead of rohkaiseva viesti?

Because here rohkaiseva viesti (encouraging message) is the object of the verb kirjoitti (wrote). As a total object, viesti appears in the genitive/accusative form viestin, and the adjective must agree:

base form (nominative): rohkaiseva viesti = an encouraging message
object form (genitive/accusative): rohkaisevan viestin = (he/she) wrote an encouraging message

So:

Puolisoni kirjoitti rohkaisevan viestin.
My spouse wrote an encouraging message.

If the noun were the subject, you’d see the nominative:

Rohkaiseva viesti auttoi minua.
The encouraging message helped me.

What is jossa, and how is it different from missä?

Jossa is a form of the relative pronoun joka (which/that, who).

joka = which / that / who
jossa = in which (inessive case of joka)

In the sentence, jossa refers back to rohkaisevan viestin:

rohkaisevan viestin, jossa hän sanoi…
= an encouraging message, in which he/she said…

Missä also means where / in which, but:

jossa specifically links to a preceding noun as a relative pronoun (standard written Finnish).
missä is originally an interrogative (where?), and in spoken language it can act like a relative, but in good written style jossa is preferred after a specific noun.

Why is there a comma before jossa?

The comma marks off a non‑restrictive relative clause.

rohkaisevan viestin, jossa hän sanoi, että…

This jossa‑clause gives extra information about the message; it doesn’t define which message out of many, it just adds detail. That’s why there is a comma, similar to English:

…an encouraging message, in which he/she said that…

If the clause were restrictive (identifying which message), the comma would usually be omitted:

Se viesti jossa oli virhe, poistettiin.
The message which had an error was deleted. (identifying which one)

Why do we need että after hän sanoi, and can it ever be left out like that in English?

Että is a conjunction that introduces a content clause, similar to English that:

hän sanoi, että pienet virheet kuuluvat oppimiseen
= he/she said that small mistakes are part of learning

Unlike English that, että is not normally omitted in standard Finnish. You can’t just say:

✗ hän sanoi pienet virheet kuuluvat oppimiseen

That sounds wrong. You need että to clearly mark the beginning of the reported clause.

Finnish punctuation also differs from English: you must put a comma before että:

sanoi, että …
(comma is obligatory before että)

Why is it pienet virheet and not pieniä virheitä?

Both are grammatically possible, but they have slightly different nuance.

pienet virheet kuuluvat oppimiseen
- pienet virheet = nominative plural
- Reads more like a general statement: small mistakes (as a type / in general) are part of learning.
pieniä virheitä kuuluu oppimiseen
- pieniä virheitä = partitive plural
- Feels more like some small mistakes or a quantity of small mistakes belong to learning.

In the given sentence, the nominative pienet virheet fits the idea of a general rule about all small mistakes in learning, so it’s a natural choice.

What does kuuluvat mean here, and why not just use ovat?

Kuulua has several meanings; here it means to belong to / to be a natural part of something.

pienet virheet kuuluvat oppimiseen
= small mistakes belong to learning / are part of learning

Using kuulua is more idiomatic than just olla (to be) when you talk about membership in a group, a category, or something being a natural element of a process.

Compare:

Se ei kuulu asiaan. = That is not relevant / that doesn’t belong to the matter.
Nämä tehtävät kuuluvat kurssiin. = These exercises are part of the course.

You could say pienet virheet ovat osa oppimista (are a part of learning), but kuulua oppimiseen is a very natural collocation.

What case is oppimiseen, and how is that form built?

Oppimiseen is the illative case singular of oppiminen (learning).

oppiminen = learning (noun)
stem: oppimise-
illative singular: oppimiseen → spelled oppimiseen (vowel contraction / spelling convention)

The illative often expresses movement into or belonging to something:

mennä kouluun = go to school
liittyä kurssiin = join a course
kuulua oppimiseen = belong to learning

So oppimiseen here means into / to learning, in the abstract sense of as part of the learning process.

Could the word order be Puolisoni kirjoitti rohkaisevan viestin minulle instead?

Yes, that word order is also correct:

Puolisoni kirjoitti minulle rohkaisevan viestin.
Puolisoni kirjoitti rohkaisevan viestin minulle.

Finnish word order is relatively flexible. Both versions mean the same thing, but there can be a slight difference in emphasis:

minulle rohkaisevan viestin (current order) can subtly highlight to me first.
rohkaisevan viestin minulle can feel a bit more like focusing on the encouraging message first, then clarifying it was to me.

In neutral context, both are fine; the original order is very typical.

Does hän refer to my spouse, and does it show gender?

Yes, hän refers back to puolisoni (my spouse).

Finnish hän is gender‑neutral:

hän = he / she (no gender distinction)

So:

Puolisoni… jossa hän sanoi…
= My spouse… in which he/she said…

If you need to indicate gender, you must rely on context or add another word (my husband, my wife), because hän itself does not change.

Could you leave out hän and just say jossa sanoi, että…?

In standard written Finnish, you normally do not drop hän in this kind of clause. You say:

jossa hän sanoi, että…

In informal spoken Finnish, people often drop third‑person pronouns when they are obvious from context:

…viestin, jossa sano, että… (spoken style)

But in correct written language, keeping hän is the norm; it makes the subject clear and matches standard grammar.

Why are there commas around the subordinate clauses (jossa…, että…) when English might not always use them?

Finnish comma rules are stricter than English ones:

Between main and subordinate clauses:
- A comma is usually placed before a subordinate clause.
- sanoi, että pienet virheet kuuluvat oppimiseen
With non‑restrictive relative clauses:
- A comma separates a non‑essential jossa‑clause from the main clause.
- rohkaisevan viestin, jossa hän sanoi, että…

So even where English could omit a comma (e.g. he said that…), Finnish requires it before että, and commonly uses it before non‑restrictive jossa/joka clauses.