Learn Hardcore Finnish: Tämä juhla on hauska.

tämä = this, something close to the speaker
tuo = that, something a bit further away, but still visible or pointed out
se = it / that, something already known from context, not physically “pointed at” anymore

Examples:

Tämä juhla on hauska. – This party (right here, that we’re at) is fun.
Tuo juhla on hauska. – That party (over there / that one we talked about) is fun.
Se juhla oli hauska. – That party (we mentioned earlier) was fun.

So tämä explicitly points to something very near or immediately present.

Why is it juhla and not juhlat here?

Juhla is the singular form: party / celebration / festival (one event).
Juhlat is the plural form: literally parties / celebrations, but in practice it often means a party as an event too (especially for private parties).

Both can be used, depending on nuance:

Tämä juhla on hauska. – This celebration/party (as an event) is fun.
Nämä juhlat ovat hauskat. – This party (these celebrations) are fun.

In your sentence, juhla treats the event more like a single “festival/celebration” rather than focusing on it as “festivities” in the plural. Both are grammatically correct; choice is stylistic.

What exactly is on here? How is it related to olla?

On is the 3rd person singular present tense form of the verb olla (to be).

Conjugation of olla in the present tense:

minä olen – I am
sinä olet – you are (singular)
hän on – he/she is
se on – it is
me olemme – we are
te olette – you are (plural / polite)
he ovat – they are
ne ovat – they are (non-human / informal)

So your sentence is literally: This party is fun.
Tämä juhla (this party) → on (is) → hauska (fun).

Why is it hauska, not hauskaa? I’ve seen both forms.

In sentences with olla (to be), an adjective describing the subject usually agrees in case and number with the subject.

Subject: Tämä juhla – nominative singular
Predicate adjective: hauska – nominative singular (matches the subject)

So:

Tämä juhla on hauska. – This party is fun.

Hauskaa is the partitive form. You see that when:

The subject is unexpressed/impersonal, and you mean “it is fun (to do something)” in general:
- On hauskaa olla täällä. – It is fun to be here.
  Here hauskaa doesn’t agree with a concrete noun; it’s more like “fun-ness” as an unbounded quality.
Some special structures (e.g., expressing partial/ongoing states) use partitive, but that’s more advanced.

For a simple X is Y sentence with a clear subject like tämä juhla, the default is nominative: hauska, not hauskaa.

Does Finnish have words like a and the? How do you know it’s this party?

Finnish has no articles like a/an or the.

Definiteness is expressed by context, word choice, and demonstratives like:

tämä = this
se = that / it
yksi can be like one / a (single) in some contexts

In Tämä juhla on hauska:

tämä already signals that we are talking about a specific, definite party: this party.

So English needs this party, but Finnish just uses tämä juhla with no extra article.

What is the grammatical structure? Which word is the subject, verb, etc.?

Breakdown of Tämä juhla on hauska:

Tämä juhla – subject noun phrase
- tämä – demonstrative pronoun (this)
- juhla – noun (party / celebration)
on – verb (is, 3rd person singular of olla)
hauska – predicate adjective (describes the subject)

So structurally:

Subject: Tämä juhla
Verb (copula): on
Predicate adjective (complement): hauska

Is Tämä on hauska juhla also correct? What’s the difference in word order?

Yes, Tämä on hauska juhla is also correct and very natural.

Tämä juhla on hauska.
- Literally: This party is fun.
- Pattern: [this party] [is] [fun]
- Slight emphasis on the fun-ness of this particular party.
Tämä on hauska juhla.
- Literally: This is a fun party.
- Pattern: [this] [is] [a fun party]
- Slightly more neutral; feels more like a simple comment when you’re at the party:
  “This is a fun party.”

In many everyday contexts, they are interchangeable, and the difference is subtle. Finnish word order is fairly flexible, and small changes mostly affect emphasis, not correctness.

What case are the words in? I don’t see any obvious case endings.

All the content words in Tämä juhla on hauska are in the nominative (the “dictionary form”):

tämä – nominative
juhla – nominative singular
hauska – nominative singular (agreeing with juhla)

The nominative often has no visible ending, especially in the singular, so it just looks like the base form from the dictionary.

The verb on is just a conjugated form of olla and doesn’t show case (verbs don’t take case endings).

Does hauska mean fun or funny?

Hauska can mean both, depending on context:

fun / enjoyable:
- Tämä juhla on hauska. – This party is fun.
- Hauskaa viikonloppua! – Have a fun weekend!
funny / amusing (makes you laugh):
- Se elokuva oli hauska. – That movie was funny/amusing.

If you want “funny” as in “strange / odd / weird,” you’d more typically use:

outo – strange, odd
kummallinen – peculiar, strange

Example:

Se on outo juttu. – That’s a strange thing.
Se on vähän kummallinen. – He/She is a bit strange.

How can I make the sentence stronger, like “really fun” or “very fun”?

Common intensifiers with adjectives like hauska:

tosi hauska – really fun
tosi kiva – really nice/fun
hyvin hauska – very fun (more formal / neutral)
erittäin hauska – extremely / very fun (formal, strong)

Examples with your sentence:

Tämä juhla on tosi hauska. – This party is really fun.
Tämä juhla on erittäin hauska. – This party is extremely fun.

How do I say it in the past tense or in the negative?

1. Past tense (was fun)

Use the past of olla: oli.

Tämä juhla oli hauska. – This party was fun.

2. Present negative (is not fun)

Use the negative verb ei + olla in the -ole form:

Tämä juhla ei ole hauska. – This party is not fun.

Conjugation of the negative for reference:

minä en ole – I am not
sinä et ole – you are not
hän ei ole – he/she is not
se ei ole – it is not
me emme ole – we are not
te ette ole – you (pl.) are not
he eivät ole – they are not

How do I pronounce juhla and hauska?

Approximate pronunciation (English-based):

juhla: YUH-hla
- j = like English y in yes
- u = like oo in food, but shorter
- h is pronounced clearly
- la as in la in lava
- Stress is on the first syllable: JUH-la
hauska: HOW-ska
- h = h
- au = like ow in cow
- s = s
- ka as in ka in karaoke
- Stress on the first syllable: HAUS-ka

Finnish always stresses the first syllable of the word.