Learn Hardcore Finnish: Pienet lapset pelaavat jalkapalloa pihalla koulun jälkeen. - Small children play football in the yard after school.

Because lapset is plural nominative, the adjective must also be plural nominative: pienet. Using pieni lapset would be grammatically wrong in standard Finnish.

What is the difference between pieni lapsi and pienet lapset?

They differ in number (singular vs. plural):

pieni lapsi = one small child
- pieni = singular adjective
- lapsi = singular noun
pienet lapset = small children (more than one)
- pienet = plural adjective
- lapset = plural noun

The meaning changes from one child to a group of children, and the adjective changes form to match that.

Why is the verb pelaavat and not pelaa?

The subject pienet lapset is third person plural, so the verb must also be in the third person plural form.

The verb is pelata (to play, a game/sport). Present tense forms:

hän pelaa = he/she plays
he pelaavat = they play

So with lapset (children, they), the correct standard form is pelaavat.

In informal spoken Finnish, people often say lapset pelaa, but in written standard Finnish you should use pelaavat.

Does pelaavat mean play or are playing?

Finnish has only one present tense form, and it covers both English present simple and present continuous.

So pelaavat can mean:

they play (habitually, regularly)
they are playing (right now)

The exact meaning comes from context. Here, with koulun jälkeen (after school), it sounds like a habitual action (something they usually do after school).

Why is jalkapalloa used instead of jalkapallo? What is that ending?

jalkapalloa is the partitive case of jalkapallo (football, soccer).

The verb pelata normally takes its object in the partitive when you are talking about playing a sport or game in general:

pelata jalkapalloa = to play football (as an activity)
pelata shakkia = to play chess
pelata tennistä = to play tennis

This is because the action is seen as open-ended / ongoing, not as a single, completed object. Using the nominative or accusative would suggest a more bounded, completed thing (like finishing one whole match), which is a different nuance and more rarely used.

So in this sentence jalkapalloa is the natural, idiomatic form.

What case is pihalla, and how is it different from pihassa or pihalle?

pihalla is in the adessive case, which usually means on, at, outside at.

piha = yard
pihalla = in/at the yard, out in the yard

Contrast with the related local cases:

pihassa (inessive) = literally in the yard (more inside a bounded space)
pihalle (allative) = to the yard (movement towards the yard)

In everyday language, pihalla is the normal way to say someone is outside in the yard area. So pihalla here means they are outside, in the yard, as a location.

Why is it koulun jälkeen and not jälkeen koulun?

jälkeen is a postposition, not a preposition. That means it normally comes after the word it depends on, and that word is in the genitive case.

koulu (school) → genitive: koulun
koulun jälkeen = after school

The order jälkeen koulun would sound wrong. The correct pattern is:

genitive + jälkeen = after X
- ruoan jälkeen = after the food/meal
- tunnin jälkeen = after the lesson

What case is koulun, and when do we use that form?

koulun is the genitive singular of koulu (school).

Genitive is used for many things, and one common use is:

with postpositions like jälkeen, ennen (before), kanssa (with), etc.

Examples:

koulun jälkeen = after school
koulun ennen is wrong → you must say ennen koulua (here ennen takes partitive instead)
ystävän kanssa = with a friend

So in this sentence, koulun is genitive because jälkeen requires it.

Can I change the word order, for example: Koulun jälkeen pienet lapset pelaavat jalkapalloa pihalla?

Yes. Finnish word order is quite flexible, and your version is grammatically correct.

Different orders mainly affect emphasis / information structure, not basic meaning. For example:

Pienet lapset pelaavat jalkapalloa pihalla koulun jälkeen.
→ Neutral: Small children play football in the yard after school.
Koulun jälkeen pienet lapset pelaavat jalkapalloa pihalla.
→ Emphasis on after school (that time frame is highlighted first).

All the following are possible with slightly different emphasis:

Pihalla pienet lapset pelaavat jalkapalloa koulun jälkeen.
Pienet lapset koulun jälkeen pelaavat jalkapalloa pihalla.

But the original order is the most neutral.

How would I make it clear that this is happening right now, not as a habit?

You can add a time adverb like nyt (now). For example:

Pienet lapset pelaavat nyt jalkapalloa pihalla koulun jälkeen.

Here nyt pushes the interpretation towards are playing right now. Without nyt, the sentence often sounds more like a general habit (they usually play after school), especially with koulun jälkeen. Context around the sentence will also influence the reading.

There is no the or a in the Finnish sentence. How do I know if it means the small children or small children in general?

Finnish does not have articles like the or a/an. The same sentence can correspond to several English versions:

Small children play football…
The small children play football…

Which one is correct in English depends on context, not on any word in the Finnish sentence. If the context has already introduced a specific group of children, English would likely use the. If it’s a general statement about children, English would drop the. Finnish leaves that distinction to context and word order, not to an explicit article.

Does pihalla always mean in the yard? I’ve heard it used differently.

Literally, pihalla is the adessive of piha, so it means in/at the yard, outside in the yard. That is the meaning in this sentence.

However, in colloquial Finnish olla pihalla can also be idiomatic and mean to be clueless / to have no idea what’s going on:

Olen ihan pihalla. = I’m totally lost / I have no idea.

In your sentence, with pienet lapset pelaavat jalkapalloa pihalla, it is clearly the literal location meaning: the children are physically playing in the yard.