Learn Hardcore Finnish: Meillä on tapana järjestää pieni elokuvailta perheen kanssa perjantaisin. - We have a habit of arranging a small movie night with the family on Fridays.

Literally, meillä means “on us / at our place / among us”.
In Finnish, possession is usually expressed with this adessive + olla structure:
- Minulla on auto. = I have a car. (literally: On me is a car.)
- Meillä on koira. = We have a dog.

In your sentence, Meillä on tapana… follows exactly the same pattern: “For us it is a habit to …” → “We usually …”

So meillä here really just encodes “we (as a group / family)”, not a physical location, even though literally it’s “on/at us”.

Why is it on tapana and not on tapa? What is tapana exactly?

Tapa is a noun meaning habit, custom, way (of doing something).
Tapana is tapa in the essive case (the -na/-nä form), often translated roughly as “as a …”.

olla tapana + infinitive is a set expression in Finnish meaning
“to be in the habit of doing X / to usually do X”.
- Minulla on tapana lukea illalla.
  = I usually read in the evening.

If you said:

Meillä on tapa järjestää pieni elokuvailta…

this is grammatically fine but sounds more like:

“We have a custom/tradition of organizing a small movie night …”

— a bit more concrete or formal, like a specific established tradition.

With on tapana, the focus is more on a regular habit in general, and it’s the most natural everyday way to say “we usually …”.

Why is the verb järjestää in the basic infinitive form and not järjestämme?

After olla tapana, Finnish uses the basic infinitive (the dictionary form) of the verb:

olla tapana + [infinitive]

So:

Meillä on tapana järjestää…
literally: “For us it is a habit to organize…”

not:

Meillä on tapana järjestämme… ❌

The subject “we” is already expressed by Meillä, and on is already conjugated (3rd person singular). So the following verb is not conjugated; it stays in the infinitive.

Compare:

Minulla on tapana juoda kahvia aamuisin.
I usually drink coffee in the mornings.

Here too, juoda is in the infinitive after on tapana.

What nuance does järjestää have here? Could you say something else instead?

Järjestää means to arrange, to organize, to put together (an event).

In this sentence it suggests:

planning the movie night,
maybe choosing the film,
setting things up (snacks, timing, etc.).

You could use other verbs:

pitää pieni elokuvailta – to hold / have a small movie night
katsoa elokuva perheen kanssa – watch a movie with the family

But:

järjestää elokuvailta sounds like “organize a movie night” as an event.
pitää elokuvailta focuses more on having / hosting it.

The given sentence presents the movie night as a little organized event.

Why is elokuvailta written as one word? What exactly does pieni elokuvailta mean structurally?

Elokuvailta is a compound noun:

elokuva = movie, film
ilta = evening
→ elokuvailta = movie night (an evening spent watching movies)

In Finnish, such combinations are normally written as one word:

koulupäivä (school day)
joulujuhla (Christmas party)

So:

pieni elokuvailta = a small movie night, where
- pieni is an adjective modifying the whole compound elokuvailta.

If you split it as elokuvan ilta, it would literally mean “the movie’s evening” and would not mean a standard “movie night” event.

Why is it pieni elokuvailta (nominative) and not something like pienen elokuvailtan or a partitive form?

Pieni elokuvailta is in the nominative singular, and in this sentence it functions as the (total) object of järjestää:

järjestää (mitä?) pieni elokuvailta
organize what? a small movie night

Finnish uses:

Nominative (or accusative) object when the event/action is seen as whole/complete:
- Järjestämme elokuvailan.
  We will organize a (specific) movie night.
Partitive object when the action is ongoing, incomplete, repeated, or unbounded:
- Järjestämme elokuvailtoja.
  We organize movie nights (in general, plural, not one specific one).

Here we’re talking about one full movie night each Friday as a habitual event, so pieni elokuvailta in nominative singular is natural.

Why is it perheen kanssa and not something like perheellä or perheessä?

Finnish often uses the postposition kanssa to express “with (someone)”:

Pattern: [genitive] + kanssa

So:

perhe → genitive perheen
perheen kanssa = with (the) family

Other cases would mean something else:

perheellä (adessive) – on/at the family (used in other structures, not “with”)
perheessä (inessive) – in the family

For “with the family”, the correct idiomatic form is perheen kanssa.

Shouldn’t it be our family, like meidän perhe? Why is there no possessive (our) in perheen kanssa?

In English you’d naturally say “with our family”, but in Finnish the possessive is often omitted when it’s clear from context.

Because the sentence starts with Meillä on tapana…, it’s obvious that:

the family referred to is “our” family.

So:

perheen kanssa is normally understood here as “with the family (ours)”.

You can make it explicit:

meidän perheen kanssa – very clear, somewhat colloquial/emphatic
perheemme kanssa – more compact, slightly more formal/neutral

All are grammatically correct, but the simple perheen kanssa is the most natural here.

What exactly does perjantaisin mean, and how is it different from perjantaina or joka perjantai?

Perjantaisin means “on Fridays / on Friday(s) in general / every Friday (as a habit)”.

Formally:

Base word: perjantai (Friday)
perjantaisin is an adverbial form built with -sin, historically from a plural case; in modern language you just learn it as an adverb of habitual time.

Differences:

perjantaisin
- on Fridays (habitually, regularly)
- matches very well with on tapana (habit).
perjantaina
- on Friday (usually a specific Friday, or “on Friday” in a more one-time sense)
- e.g. Tapaamme perjantaina. – We’ll meet on Friday (this/that one).
joka perjantai
- literally “every Friday”; very clear, explicit.
- Often interchangeable with perjantaisin, but a bit more emphatic.

So in the sentence about a standing family habit, perjantaisin is the most natural choice.

Can the word order be changed? For example, can I say Meillä on tapana perjantaisin järjestää pieni elokuvailta perheen kanssa?

Yes, Finnish word order is relatively flexible, and several variants are natural. For example:

Meillä on tapana järjestää perheen kanssa pieni elokuvailta perjantaisin. (original)
Meillä on tapana perjantaisin järjestää pieni elokuvailta perheen kanssa.
Perjantaisin meillä on tapana järjestää pieni elokuvailta perheen kanssa.

All are grammatical. The differences are in emphasis:

Starting with Perjantaisin emphasizes the time: “On Fridays, we tend to…”
Moving perjantaisin earlier highlights the habitual timing a bit more.

The original order is very natural and neutral; the alternatives just shift what’s slightly more in focus.

Could you also say Me järjestämme pienen elokuvaillan perjantaisin? How is that different from Meillä on tapana järjestää pieni elokuvailta perjantaisin?

Yes, you can say:

Me järjestämme pienen elokuvaillan perjantaisin.

This is perfectly correct and means essentially the same thing. The nuance:

Me järjestämme…
- Simple factual statement: “We organize a small movie night on Fridays.”
Meillä on tapana järjestää…
- Explicitly presents it as a habit or customary practice: “We usually / We tend to organize a small movie night on Fridays.”

So the on tapana version foregrounds the idea of a regular habit, while the simple Me järjestämme… just states what you do, with the regularity implied only by perjantaisin.