Learn Hardcore Finnish: Tämä kurssi on minulle suuri ilo.

In the phrase on minulle suuri ilo, the idea is this course is a great joy to me / for me, so Finnish uses the allative case minulle to show to whom the joy belongs or for whom it is a joy.

What grammatical roles do Tämä kurssi, on, minulle, and suuri ilo have?

Tämä kurssi = subject (in nominative case)
this course
on = verb olla (to be), 3rd person singular present
is
minulle = indirect experiencer/beneficiary in allative case
to me / for me
suuri ilo = predicative noun phrase (also nominative) describing the subject
a great joy

So structurally it’s:

[Subject] Tämä kurssi
[Verb] on
[Experiencer] minulle
[Predicative] suuri ilo

Could you also say Tämä kurssi on suuri ilo minulle? Is that different?

Yes, you can say:

Tämä kurssi on suuri ilo minulle.

Both Tämä kurssi on minulle suuri ilo and Tämä kurssi on suuri ilo minulle are correct and mean the same thing.

The word order difference is subtle:

on minulle suuri ilo: slightly highlights the personal aspect (for me, this is a great joy).
on suuri ilo minulle: slightly highlights what the course is first (a great joy), and then adds for me.

In everyday speech, both are natural, and the difference is mostly about nuance and emphasis.

Why is suuri used here instead of iso? Aren’t they both “big”?

Both suuri and iso can mean big, but they differ in style and typical usage.

iso = big (more colloquial, physical size, everyday speech)
suuri = big/great (slightly more formal or abstract)

With an abstract noun like ilo (joy), suuri ilo feels more natural, a bit more elevated, like great joy or great pleasure.

You could say iso ilo, and people would understand, but suuri ilo is the more idiomatic choice in this kind of sentence.

Why is ilo in the basic form and not inflected, like ilon or iloa?

Ilo is in the nominative singular here because it is the predicative noun – it describes what the subject Tämä kurssi is.

In Finnish, with the verb olla (to be), both the subject and the predicative are typically in the nominative:

Kurssi on ilo. – The course is a joy.
Tämä kurssi on suuri ilo. – This course is a great joy.

Forms like:

ilon = of the joy (genitive)
iloa = some joy, joy (partitive)

would be used in different contexts, for example with different verbs or meanings.

Why doesn’t Finnish have an article like “a” in “a great pleasure”?

Finnish simply doesn’t use articles (no a/an or the) at all.

So:

suuri ilo can mean a great joy, the great joy, or just great joy, depending on context.

English listeners automatically supply an article when translating. The Finnish structure Tämä kurssi on minulle suuri ilo doesn’t need any extra word to express a.

Can Tämä kurssi be shortened to just Tämä here?

In some contexts, yes:

If everyone already clearly knows you are talking about a course, you might say:
- Tämä on minulle suuri ilo. – This is a great joy for me.

However, in a neutral teaching example, Tämä kurssi makes it clear what this refers to. Including kurssi removes ambiguity.

Is the word order fixed, or can I move things around?

Finnish word order is relatively flexible, and you can rearrange the sentence for emphasis while keeping the meaning.

All of these are grammatically correct:

Tämä kurssi on minulle suuri ilo.
Tämä kurssi on suuri ilo minulle.
Minulle tämä kurssi on suuri ilo.
Suuri ilo tämä kurssi on minulle. (more poetic/emphatic)

The basic “neutral” order in everyday use would be one of the first two. Moving minulle or suuri ilo to the front adds emphasis to those parts.

Could I express the same idea with a verb like “delight” instead of “to be joy”?

Yes, Finnish has other ways to express the same idea. For example:

Tämä kurssi ilahduttaa minua.
This course delights me / makes me happy.

Here:

ilahduttaa = to delight, to cheer up
minua = me (partitive form of minä)

The meaning is similar, but Tämä kurssi on minulle suuri ilo sounds slightly more formal or emotional, like giving a value judgment: This course is a great joy to me.

What is the difference between ilo, mukava, and kiva in similar sentences?

ilo = joy, delight (a noun; more emotional, a bit more elevated)
- Tämä kurssi on minulle suuri ilo. – This course is a great joy to me.
mukava = nice, pleasant, comfortable (an adjective)
- Tämä kurssi on minulle mukava. – This course is nice/pleasant for me.
kiva = nice, fun (very colloquial)
- Tämä kurssi on minulle tosi kiva. – This course is really nice/fun for me.

Using ilo emphasizes an inner feeling of joy; mukava/kiva are more casual judgments about how nice something is.

Why do both Tämä kurssi and suuri ilo appear in the same (nominative) form? Doesn’t one of them need a special case?

With the verb olla (to be), it’s normal in Finnish for:

the subject and
the predicative noun/adjective

to both be in the nominative case when the meaning is X is Y:

Tämä kurssi (subject, nominative)
suuri ilo (predicative, nominative)

Examples:

Helsinki on suuri kaupunki. – Helsinki is a big city.
Tämä kirja on hyvä. – This book is good.
Tämä kurssi on suuri ilo. – This course is a great joy.

So in this pattern, nominative for both is the standard choice.