Learn Hardcore Finnish: Heillä ei ole tapana myöhästyä, vaikka bussi on useimmiten täynnä. - They don’t usually arrive late, even though the bus is most often full.

He eivät yleensä myöhästy = They usually don’t (tend to) be late.
– Focus on the action: they (generally) don’t arrive late.
Heillä ei ole tapana myöhästyä = They are not in the habit of being late.
– Focus on the habit: being late is not characteristic of them.

So the structure olla tapana + infinitive (to be in the habit of doing X) makes it sound a bit more like you’re talking about their established habits or typical behavior, not just statistical frequency.

What exactly is tapana, and why is it in that form?

Tapana is the essive case of tapa (“habit, custom, way”).

tapa = habit, custom
tapana ≈ “as a habit”, “as a way (of behaving)”

The fixed expression is:

olla tapana + infinitive = to be in the habit of doing X

So:

Heillä on tapana myöhästyä = They have a habit of being late.
Heillä ei ole tapana myöhästyä = They do not have a habit of being late.

This pattern with the essive appears in other expressions too, like:

on tapana sanoa = it is customary to say / it is often said

Why is it Heillä and not just He in Heillä ei ole tapana myöhästyä?

Heillä is the adessive case of he (“they”).

he = they (nominative)
heillä ≈ “on them”, “at them” (adessive)

Finnish often expresses possession with:

[Adessive possessor] + on/ei ole + [thing possessed]
literally: At them is / is not X → They have / do not have X

So:

Heillä on koira. = They have a dog.
Heillä ei ole koiraa. = They don’t have a dog.
Heillä ei ole tapana myöhästyä. = They are not in the habit of being late.

Here, the “thing possessed” is the habit (tapana myöhästyä), and heillä marks who (does or does not) have that habit.

In Heillä ei ole tapana myöhästyä, why is it ei ole and not eivät ole, since he is plural?

In this type of sentence, olla is used in a possessive / existential structure, and it agrees with the “thing possessed”, not with the possessor.

The “possessor” is heillä (adessive) – not the grammatical subject.
The thing that “exists / is had” is tapana myöhästyä, which is singular.

Therefore we use third-person singular:

Heillä on tapana myöhästyä. = They have a habit of being late.
Heillä ei ole tapana myöhästyä. = They do not have a habit of being late.

Compare:

He ovat myöhässä. = They are late. (subject he, verb ovat)
Heillä on kiire. = They are in a hurry. (literally “at them is hurry” → verb on, not ovat)

So eivät ole would be wrong here because we’re not saying “they are not”; we’re saying “they do not have”.

Why is myöhästyä in the infinitive, not a conjugated form like myöhästy or myöhästyvät?

After olla tapana, Finnish uses the first infinitive (myöhästyä = “to be late”).

Pattern:

olla tapana + [1st infinitive]

Examples:

Minulla on tapana lukea iltaisin. = I have a habit of reading in the evenings.
Onko sinulla tapana juoda kahvia aamulla? = Do you usually drink coffee in the morning?

So myöhästyä is the dictionary form (“to be late”) used as the action that is or isn’t a habit.

What does vaikka mean in this sentence? Is it “although” or “even if”?

In this context, vaikka means “although / even though”.

Heillä ei ole tapana myöhästyä, vaikka bussi on useimmiten täynnä.
≈ They are not in the habit of being late, although the bus is usually full.

Here, we are talking about a real, known situation (the bus really is usually full), so “although / even though” is the best translation.

When vaikka introduces something hypothetical, it can lean more toward “even if”:

Tulen, vaikka sataa. = I’ll come, even if it rains.

In your sentence it describes a real, frequent condition, so read it as “although / even though”.

Can the word order in vaikka bussi on useimmiten täynnä be changed, for example vaikka bussi useimmiten on täynnä?

Yes, some variation is possible, but the given order is the most natural and neutral:

vaikka bussi on useimmiten täynnä (most natural)
vaikka bussi useimmiten on täynnä (possible, slightly marked / more emphatic on “is (indeed) usually full”)
vaikka useimmiten bussi on täynnä (also possible, but sounds more stylized or contrastive)

In everyday language, subject – verb – adverb – complement (as in the original) is very typical:

bussi on useimmiten täynnä

What’s the difference between useimmiten and yleensä? Could we say vaikka bussi on yleensä täynnä instead?

Both useimmiten and yleensä refer to frequency, but with slightly different nuances.

useimmiten ≈ most of the time, in most cases
– Focus on how often something happens (in a majority of cases).
yleensä ≈ generally, typically, in general
– Focus on what is typical / normal, not strictly on frequency count.

In your sentence, both work:

vaikka bussi on useimmiten täynnä
vaikka bussi on yleensä täynnä

The first sounds a bit more like: on most days / in most cases the bus is full.
The second: as a general rule, the bus is (pretty) full.

Why is it täynnä and not täysi in bussi on useimmiten täynnä?

Täynnä is the usual predicative form used with olla to mean “full (of something)”.

Bussi on täynnä. = The bus is full.
Bussi on täynnä ihmisiä. = The bus is full of people.

Grammatically, täynnä is the essive form of täysi (“full”), but in practice, “olla täynnä (jotakin)” is treated like a fixed pattern:

olla täynnä + partitive = “be full of X”

The form täysi is more like a plain attributive adjective:

täysi bussi = a full bus
täysi lasi = a full glass

So:

predicate: bussi on täynnä
attribute: täysi bussi

Why is bussi in the basic form (nominative) in bussi on useimmiten täynnä?

Here bussi is the subject of the clause, so it appears in the nominative singular:

Bussi on täynnä. = The bus is full.
– subject: bussi
– verb: on
– predicative: täynnä

There’s no reason to use any other case:

We are not marking movement (bussiin), location (bussissa), etc.
We are simply saying what the bus is like.

So nominative subject + olla + description is the basic pattern.

Can I say Heillä ei ole myöhästyä and just drop tapana?

No, Heillä ei ole myöhästyä is ungrammatical.

The pattern [adessive] + on/ei ole + [noun or noun phrase] needs a noun-like thing after on/ei ole:

Heillä on koira.
Heillä ei ole koiraa.
Heillä on tapana myöhästyä.

Here, tapana myöhästyä works as a kind of noun phrase: “a habit (of being late)”.

The infinitive myöhästyä alone is just a verb form (“to be late”), not something you can “have” without a supporting noun like tapa.

Is Heillä ei ole tapana myöhästyä formal, neutral, or colloquial? Are there more everyday alternatives?

Heillä ei ole tapana myöhästyä is neutral standard Finnish. It’s perfectly fine in spoken language, but it can sound a tiny bit more careful / literary than some simpler alternatives.

Everyday alternatives expressing roughly the same idea:

He eivät yleensä myöhästy. = They usually don’t get late.
He eivät oikeastaan koskaan myöhästy. = They pretty much never are late.
He eivät ole tapana myöhästellä. (less common, slightly off; better with olla tapana
- infinitive as in the original)

The original sentence is natural and not stiff, so you can safely use it in most contexts (spoken or written).

Could I use myöhästellä instead of myöhästyä, and what’s the difference?

Yes, you could say:

Heillä ei ole tapana myöhästellä, vaikka bussi on useimmiten täynnä.

Myöhästyä and myöhästellä are related but not identical:

myöhästyä = to be late (once, to be delayed)
– more punctual, event-like.
myöhästellä = to be late repeatedly / to dawdle / to be in the habit of being late
– frequentative, emphasizes repetition or a somewhat careless attitude.

Since olla tapana already expresses habit, both work, but:

olla tapana myöhästellä sounds especially like a bad, repeated habit.
olla tapana myöhästyä is a bit more neutral: simply “to be in the habit of being late”.

In your sentence, either is acceptable, but myöhästyä is slightly more neutral.