Suutari huomasi, että kengän kantapää on rikki ja toisessa kengässä on pieni reikä.

Because että introduces a subordinate clause, roughly like English that.

• Suutari huomasi = the cobbler noticed
• että ... = that ...

In standard Finnish, a subordinate clause is normally separated from the main clause with a comma, so huomasi, että ... is the expected punctuation.

Here että means that.

So the structure is:

• Suutari huomasi = The cobbler noticed
• että kengän kantapää on rikki... = that the shoe’s heel is broken...

In everyday English, that is often omitted, but in Finnish että is very commonly stated.

Kengän is the genitive singular of kenkä.

The genitive is used here to show possession or a close relationship:

• kenkä = shoe
• kengän kantapää = the shoe’s heel / the heel of the shoe

So kengän answers the question whose heel? → the shoe’s.

This is a normal stem change in Finnish, called consonant gradation.

The dictionary form is:

• kenkä = shoe

But in many other forms, the stem changes to kengä-:

• kengän = of the shoe
• kengässä = in the shoe

So this is not an irregular surprise you just have to memorize separately; it is part of a common Finnish pattern.

Because kantapää is the main noun of the phrase, and here the whole phrase is the subject of on rikki.

• kengän = of the shoe
• kantapää = heel

So literally:

• kengän kantapää on rikki = the shoe’s heel is broken

Only the first noun, kengän, shows the possessor. The main noun kantapää stays in the form required by the sentence, which here is the basic nominative form.

Kantapää means heel.

It can refer to:

• the heel of a foot
• the heel of a shoe

In this sentence, the context makes it clear that it means the heel of the shoe.

It is also a compound word:

• kanta = heel/base/back part
• pää = head/end

You do not need to translate the parts literally here; just learn kantapää as the normal word for heel.

On rikki means is broken.

• on = is
• rikki = broken, in pieces, out of order

Finnish often uses olla + rikki to describe something that is broken:

• Puhelin on rikki = The phone is broken.
• Kengän kantapää on rikki = The shoe’s heel is broken.

A useful nuance:

• rikki usually describes the state of being broken
• rikkinäinen is more like broken/damaged as an adjective describing the item itself

So on rikki is very natural here.

Because toisessa kengässä means in the other shoe.

• toinen = the other / second
• toisessa = in the other / in the second
• kengässä = in the shoe

Both words are in the same case because toinen agrees with the noun it modifies.

The case here is the inessive, which often means in:

• kengässä = in the shoe
• toisessa kengässä = in the other shoe

Here it most naturally means the other.

When Finnish talks about two things, toinen often means the other one:

• toinen kenkä = the other shoe

So:

• toisessa kengässä on pieni reikä = there is a small hole in the other shoe

In other contexts, toinen can also mean second, but here other is the best interpretation because we are clearly talking about a pair of shoes.

Finnish does not always shift tenses the same way English does.

The main verb is past:

• huomasi = noticed

But the things noticed are presented as states:

• kantapää on rikki = the heel is broken
• toisessa kengässä on pieni reikä = there is a small hole in the other shoe

This is natural if the speaker is reporting what the cobbler noticed as a fact that was true at that moment, and possibly still true. English often says was broken, but Finnish can comfortably use the present in this kind of subordinate clause.

You could also see past forms in some contexts, but the sentence as given is completely normal.

Because this is an existential-type sentence: it introduces the existence of something somewhere.

Finnish often uses the pattern:

• [place] + on + [thing]
• literally: in the other shoe is a small hole

So:

• toisessa kengässä on pieni reikä = there is a small hole in the other shoe

This word order is very common when you mean there is / there are.

If you said pieni reikä on toisessa kengässä, it would sound more like you are emphasizing the small hole as the topic.

Because in toisessa kengässä on pieni reikä, reikä is the thing that exists, and with a singular count noun, Finnish usually uses the nominative in this pattern.

• reikä = a hole
• pieni reikä = a small hole

Compare:

• Kengässä on reikä. = There is a hole in the shoe.
• Kengässä on reikiä. = There are holes in the shoe.

In the second example, the plural indefinite noun becomes partitive: reikiä.

Because the sentence refers to each shoe separately.

• kengän kantapää = the heel of one shoe
• toisessa kengässä = in the other shoe

English often does something similar:

• the heel of the shoe is broken, and the other shoe has a small hole

So Finnish is not talking about shoes in general; it is talking about two individual shoes in a pair.