Learn Hardcore Finnish: Kasviskeitto on herkullista.

Herkullinen is the basic (dictionary) form of the adjective delicious.
In this sentence it appears as herkullista, which is the partitive singular form.

With the verb olla (to be), Finnish can put the describing word (the predicate adjective) either in:

nominative: herkullinen
partitive: herkullista

The partitive is used here because kasviskeitto is being thought of as an unbounded substance / mass (like “some vegetable soup”, “vegetable soup in general”), not as one countable item.

So:

Kasviskeitto on herkullista.
= Vegetable soup (as a kind / as a mass) is delicious.

If you used herkullinen (nominative), it would more naturally refer to one specific, countable soup (e.g. one particular pot or bowl).

When would I say Kasviskeitto on herkullinen instead?

Kasviskeitto on herkullinen is also correct, but it tends to mean:

This particular vegetable soup is delicious,
usually referring to a specific dish, pot, or serving you’re talking about.

A rough guide:

Kasviskeitto on herkullista.
→ talking about vegetable soup as a type / in general / as a mass.
Kasviskeitto on herkullinen.
→ talking about one identifiable soup dish (for example, the vegetable soup we’re eating now).

Context and intonation also affect how people interpret it, but that’s the typical difference.

Why does Finnish use the partitive case to describe food like this?

Finnish often uses the partitive when talking about:

Uncountable substances (milk, wine, soup, chocolate, etc.)
An indefinite amount (“some x”)
Things in general, not as separate distinct items

Food and drink are very often treated as mass nouns, so you get patterns like:

Maito on hyvää. – Milk is good.
Kahvi on kuumaa. – Coffee is hot.
Keitto on suolaista. – The soup is salty.
Kasviskeitto on herkullista. – Vegetable soup is delicious.

In all these, the describing word (hyvää, kuumaa, suolaista, herkullista) is in the partitive singular, matching the idea of a mass/substance.

Why doesn’t Finnish use any article like “the” or “a” in this sentence?

Finnish simply doesn’t have articles like a, an, the. The bare noun kasviskeitto can mean:

vegetable soup in general
a vegetable soup
the vegetable soup

Which one you mean is decided by context, not by a separate word.

So Kasviskeitto on herkullista can be understood as:

“Vegetable soup is delicious” (general statement), or
“(The) vegetable soup is delicious” (in a suitable context, e.g. at a restaurant talking about the soup of the day).

How would I clearly say “The vegetable soup is delicious” in Finnish?

Most of the time, you still just say:

Kasviskeitto on herkullista.
or
Kasviskeitto on herkullinen.

Context and situation make it clear that you’re talking about the specific soup (for example, when everyone knows which soup is meant).

If you really want to stress this particular vegetable soup, you can add a demonstrative:

Tämä kasviskeitto on herkullista / herkullinen.
= This vegetable soup is delicious.

Or specify more:

Ravintolan kasviskeitto on herkullista.
= The restaurant’s vegetable soup is delicious.

But there is no separate word for the; you use other tricks (like tämä, possessives, context).

Why is kasviskeitto in basic form, but herkullista has an ending?

In this sentence:

Kasviskeitto is the subject. Subjects are usually in the nominative (basic form), so no ending appears.
Herkullista is a predicative adjective (the thing describing the subject after on). Here it’s in the partitive case for the “mass / general” meaning.

So structurally:

[Kasviskeitto] (subject, nominative)
[on] (verb “is”)
[herkullista] (predicative adjective, partitive)

The noun doesn’t need a special ending just to be the subject; the adjective needs an ending because case is expressing that nuanced meaning (mass / general).

Is herkullista an adjective or an adverb here?

It’s an adjective, not an adverb.

The basic adjective is herkullinen (delicious).
herkullista is its partitive singular form.

Finnish adjectives change form to match case and number. Here, the adjective is in the partitive, describing the state of the subject, not modifying the verb like an adverb would.

So structurally it’s like English “delicious”, not “deliciously”.

Can I change the word order? For example, can I say Herkullista on kasviskeitto?

Yes, you can say:

Herkullista on kasviskeitto.

Grammatically it’s fine. The meaning is still “Vegetable soup is delicious,” but the focus changes:

Kasviskeitto on herkullista.
→ neutral, ordinary statement.
Herkullista on kasviskeitto.
→ sounds a bit more stylistic/emphatic, like “What’s delicious is the vegetable soup.”

Normal, everyday speech usually uses the original order Subject – Verb – Complement:

Kasviskeitto on herkullista.

How do I say “Vegetable soups are delicious” in Finnish?

You make both the subject and the adjective plural:

Kasviskeitot ovat herkullisia.

Breakdown:

kasviskeitot = vegetable soups (nominative plural; -t ending)
ovat = are (3rd person plural of olla)
herkullisia = delicious (partitive plural of herkullinen)

So plural sentence:

Kasviskeitto on herkullista. – Vegetable soup is delicious.
Kasviskeitot ovat herkullisia. – Vegetable soups are delicious.

How do you pronounce kasviskeitto on herkullista?

Approximate English-friendly guide (stressed syllable in CAPS):

KAS-vis-kei-tto on HER-kul-lis-ta

Details:

Stress is always on the first syllable of each word: KAS-vis, KEI-tto, HER-kul-lis-ta.
kas like “cuss” (but with a slightly harder k-s sound at the end).
vis like “vis” in “visible”.
kei like “kay”.
tto like “t-toh” with a long /tt/; you really hold the t slightly longer.
on like English “on” but shorter.
her similar to English “hair” but shorter and without the diphthong.
kul like “cool” but with a short vowel /u/.
lis like “lease” but very short.
ta like “tah”.

Double consonants (tt, kk, ll, ss) are genuinely held longer in Finnish, which can change meaning, so try to lengthen them a bit.

How can I make this sentence stronger, like “Vegetable soup is really/very delicious”?

You can add an intensifier before herkullista:

Kasviskeitto on todella herkullista. – Vegetable soup is really delicious.
Kasviskeitto on tosi herkullista. – Vegetable soup is really/so delicious. (more colloquial)
Kasviskeitto on erittäin herkullista. – Vegetable soup is very / extremely delicious.

The structure stays the same:

Kasviskeitto + on + (intensifier) + herkullista.