Learn Hardcore Finnish: Tämä on kahvila, jossa opiskelen suomea.

Rule: A comma is normally placed between the main clause and any subordinate clause, including relative clauses with joka / jossa / jota etc.
- Tämä on kahvila, jossa opiskelen suomea.
  → main clause: Tämä on kahvila
  → subordinate (relative) clause: jossa opiskelen suomea
In English, you might write This is the café where I study Finnish (no comma) because it is a restrictive relative clause. Finnish does not make the same comma/no-comma distinction between restrictive and non‑restrictive relative clauses.

So the comma here is required in standard written Finnish; leaving it out would be considered incorrect or at least a serious punctuation mistake.

What exactly does jossa mean, and how is it formed?

Jossa is a relative pronoun meaning roughly in which / where.

Its dictionary form is joka (which / who / that).
Finnish relative pronouns change form to show case, just like nouns do.

Breakdown:

joka = which / who / that
-ssa = in (the inessive case ending)
joka + ssa → jossa = in which (used here as where)

So:

Tämä on kahvila, jossa opiskelen suomea.
Literally: This is a café in which I study Finnish.

The whole phrase jossa opiskelen suomea is a clause that modifies kahvila and tells you which café it is.

Why is it jossa and not missä? Both can be translated as where, right?

Both can translate to English where, but they are different types of words in Finnish:

missä = question word / interrogative adverb
- Used to ask: Missä opiskelet suomea? – Where do you study Finnish?
jossa = relative pronoun (from joka in inessive case)
- Used to link a noun to a clause describing it:
  Tämä on kahvila, jossa opiskelen suomea. – This is the café where I study Finnish.

In standard Finnish, you:

Use missä to ask about a place.
Use jossa (or another form of joka) to refer back to a place already mentioned.

In colloquial spoken Finnish, people sometimes say things like:

Tämä on kahvila, missä opiskelen suomea.

This is common in speech, but in careful written Finnish jossa is preferred.

Why is kahvila in the basic form, not kahvilassa (in the café)?

Kahvila here is in the nominative case, because it is the predicative of the verb olla (to be):

Tämä on kahvila. – This is a café.

This is an identity / classification sentence: it tells you what this is, not where it is. In Finnish, after olla in this sense, the complement usually stays in the nominative:

Hän on opettaja. – He/She is a teacher.
Tämä on talo. – This is a house.
Tämä on kahvila. – This is a café.

The location information (the idea of “in the café”) is expressed inside the relative clause by jossa:

jossa = in which (in that café)

If you said Tämä on kahvilassa, it would mean something like:

This is in the café (for example, pointing at an object that is located in a café)

So:

Tämä on kahvila, jossa opiskelen suomea.
= This is the café where I study Finnish (classifying what it is)
Tämä on kahvilassa.
= This is in the café (telling where “this” is)

What case is suomea, and why isn’t it just suomi?

Suomea is the partitive singular of suomi.

suomi (nominative) – Finnish (as a language)
suomea (partitive) – Finnish (as an ongoing, not‑completed object)

With verbs like opiskella (to study), puhua (to speak), ymmärtää (to understand) etc., the language is usually in the partitive:

Opiskelen suomea. – I study Finnish / I am studying Finnish.
Puhun suomea. – I speak Finnish.
Ymmärrän vähän suomea. – I understand a little Finnish.

Why partitive?

The partitive often marks:
- an ongoing, incomplete activity or
- an indefinite amount of something.

Studying a language is an open‑ended process; you are not completing all of Finnish in one go. So suomea fits the typical use of the partitive.

Compare:

Opin suomen. – I learned Finnish (fully; I mastered it).
Opiskelen suomea. – I study Finnish (ongoing process).

Why is suomea written with a lowercase s?

In Finnish:

Names of countries and proper nouns are capitalized:
- Suomi – Finland (the country)
- Ruotsi – Sweden
Names of languages are not capitalized:
- suomi – the Finnish language
- ruotsi – the Swedish language

So:

Olen Suomesta. – I am from Finland.
Puhun suomea. – I speak Finnish.

In your sentence:

suomea is the partitive of suomi meaning the language, so it is written with a lowercase s.

How is opiskelen formed from opiskella, and what tense is it?

Opiskelen is the 1st person singular present tense of the verb opiskella (to study).

Stem and ending:

Infinitive: opiskella – to study
Verb stem (present): opiskele-
1st person singular ending: -n

So:

opiskele- + n → opiskelen – I study / I am studying

Present tense conjugation of opiskella:

minä opiskelen – I study
sinä opiskelet – you (sg) study
hän opiskelee – he/she studies
me opiskelemme – we study
te opiskelette – you (pl) study
he opiskelevat – they study

Important note: Finnish has one present tense, which covers both English simple present and present progressive:

Opiskelen suomea.
= I study Finnish or I am studying Finnish.

Could I use opin instead of opiskelen? What is the difference between opiskella and oppia?

They are related but not the same:

opiskella = to study (the process of studying)
oppia = to learn (the result or gaining of knowledge/skill)

In your sentence, opiskelen suomea is natural:

Tämä on kahvila, jossa opiskelen suomea.
– This is the café where I study Finnish.

If you say opin suomea, it leans more toward the idea that you are actually learning / picking up Finnish, not just that you spend time studying:

Opin suomea nopeasti. – I am learning Finnish quickly.
Olen oppinut paljon suomea. – I have learned a lot of Finnish.

So:

Use opiskelen suomea when you want to say I study Finnish (habit, activity, place where you study).
Use forms of oppia when you want to emphasize that you have learned or are learning successfully.

Why is it Tämä on kahvila and not Se on kahvila or Tuo on kahvila?

Finnish has three basic demonstratives:

tämä – this (near the speaker)
tuo – that (farther away, often visible)
se – that / it (more neutral, often already known from context)

Rough guidelines:

tämä: introducing something right here, close to you, often new in the conversation.
- Tämä on kahvila. – This is a café. (e.g. pointing to the place you are in or right next to)
tuo: pointing at something over there, a bit away.
- Tuo on kahvila. – That (over there) is a café.
se: referring to something already known, or when physical distance is not important.
- Se kahvila on hyvä. – That café is good. (you both know which one)

In your sentence:

Tämä on kahvila, jossa opiskelen suomea.
suggests you are introducing or presenting this specific café (perhaps one that you are currently indicating), so tämä is natural.

You could say:

Se on se kahvila, jossa opiskelen suomea. – That is the café where I study Finnish.
Here se would refer to a café already mentioned or understood from context.

Can I change the word order, for example to Tässä kahvilassa opiskelen suomea or Opiskelen suomea tässä kahvilassa? Do they mean the same thing?

They are all grammatical, but they emphasize different things.

Tämä on kahvila, jossa opiskelen suomea.
– This is the café where I study Finnish.
- Focus: identification / definition of the café.
Tässä kahvilassa opiskelen suomea.
– In this café I study Finnish.
- Focus: location (this particular café) as the place of your studying.
- There is no relative clause; it is one simple sentence.
Opiskelen suomea tässä kahvilassa.
– I study Finnish in this café.
- Focus: what you do (studying Finnish), with the place as extra information.

So, the core meaning (you + café + studying Finnish) is similar, but:

The original sentence uses a relative clause to define the café.
The others are plain statements about where you do your studying.

What kind of clause is jossa opiskelen suomea, and how does it work?

Jossa opiskelen suomea is a relative clause.

It is introduced by jossa, a form of joka, which refers back to kahvila.
Inside the clause, there is a full sentence structure:
- (minä) opiskelen suomea
- The subject minä (I) is just omitted, which is normal in Finnish.

Function:

It modifies the noun kahvila, telling you which café it is:
- kahvila, jossa opiskelen suomea
  = the café in which I study Finnish / the café where I study Finnish

In English terms, this is very close to a defining relative clause with where:

This is the café where I study Finnish.

Could I drop jossa and just say Tämä on kahvila, opiskelen suomea?

No, not in standard Finnish. You need something to link the two parts.

Tämä on kahvila, opiskelen suomea.
would be seen as two independent clauses wrongly joined with just a comma (a kind of “comma splice”), and the relationship between them would be unclear.

Correct options:

Use a relative clause (your original sentence):
- Tämä on kahvila, jossa opiskelen suomea.
Make two separate sentences:
- Tämä on kahvila. Opiskelen täällä suomea.
  (This is a café. I study Finnish here.)
Connect them with a conjunction and an adverb:
- Tämä on kahvila, ja opiskelen täällä suomea.
  (This is a café, and I study Finnish here.)

Also note the difference between jossa and siellä / täällä:

jossa = in which; must refer back to a specific noun (kahvila)
siellä / täällä = there / here; more general adverbs of place

So you cannot simply remove jossa without changing the structure; you must replace it with something appropriate for the new sentence pattern.