Tässä sanassa on yksi kirjain liikaa.

Tässä is the inessive form of tämä (this), and it means in this or here in this.

So:

• tämä = this
• tässä = in this / here

In this sentence, tässä goes together with sanassa:

• tässä sanassa = in this word

This form is not built in a completely transparent way from tämä, so it is best learned as a common case form:

• tämä → tässä = in this
• tämä → tästä = from this
• tähän = into this

Finnish uses these case forms very often instead of separate words like English in, from, to.

The ending -ssa / -ssä is the inessive case, which usually means in.

So:

• sana = word
• sanassa = in the word

In the full phrase:

• tässä sanassa = in this word

Finnish often expresses location with case endings instead of separate prepositions. English says in this word, but Finnish says something more like this-in word-in.

The vowel harmony here gives -ssa rather than -ssä, because sana has the back vowels a.

Yes, both carry an in idea, but they do different jobs.

• tässä = in this
• sanassa = in the word

Together they form one noun phrase:

• tässä sanassa = in this word

This is normal in Finnish. The demonstrative and the noun often agree in case.

Compare:

• tämä sana = this word
• tässä sanassa = in this word
• tästä sanasta = from this word

So both words show the same case because they belong together.

Yes. This is a very common Finnish structure: an existential sentence.

Pattern:

• [place/location] + on + thing

So here:

• Tässä sanassa = in this word
• on = there is / is
• yksi kirjain liikaa = one letter too many

Literally, it works like:

• In this word is one letter too many

Natural English would usually say:

• There is one letter too many in this word

Finnish often puts the location first and then uses on.

More examples:

• Pöydällä on kirja. = There is a book on the table.
• Huoneessa on kaksi ikkunaa. = There are two windows in the room.

Because after yksi (one), the noun is singular, and in this sentence it appears in the basic singular form kirjain.

So:

• yksi kirjain = one letter

This is different from numbers 2 and up, where Finnish usually uses the partitive singular:

• yksi kirjain = one letter
• kaksi kirjainta = two letters
• kolme kirjainta = three letters

So yksi behaves differently from larger numbers.

Also, kirjain is one of those Finnish nouns whose basic form ends in -n:

• kirjain = letter
• stem in other forms: kirjaime- / kirjaim-
• for example: kirjainta, kirjaimen, kirjaimessa

Liikaa means too much, too many, or excessively, depending on context.

In this sentence:

• yksi kirjain liikaa = one letter too many

So liikaa marks that the amount is excessive.

You can use it with many kinds of things:

• liikaa suolaa = too much salt
• liikaa ihmisiä = too many people
• kaksi euroa liikaa = two euros too much
• yksi kirjain liikaa = one letter too many

A useful way to think about it is:

• liikaa = more than is correct / more than needed

Because in Finnish, expressions like one too many, two too many, five too much, and so on often place liikaa after the quantity expression.

So:

• yksi kirjain liikaa = one letter too many
• kaksi päivää liikaa = two days too many
• 10 euroa liikaa = 10 euros too much

This is the normal order.

If you translated word-for-word into English order, it might feel unusual, but in Finnish this placement is very natural.

Yes, and that is a useful comparison.

• Tässä sanassa on yksi kirjain liikaa. = There is one letter too many in this word.
• Tässä sanassa on liikaa kirjaimia. = There are too many letters in this word.

The difference is specificity:

• yksi kirjain liikaa gives the exact excess amount: one
• liikaa kirjaimia just says the number of letters is excessive, without saying by how much

So the original sentence is more precise.

Because the sentence is not saying too many letters in a general way. It is saying one letter too many, which is a more exact amount.

Compare:

• liikaa kirjaimia = too many letters
• yksi kirjain liikaa = one letter too many

The first focuses on an excessive plural quantity. The second focuses on the exact amount of excess.

So the singular kirjain is correct because the number is exactly one.

Yes, but the emphasis changes.

The original:

• Tässä sanassa on yksi kirjain liikaa.

This is the most neutral way to say it.

You could also say:

• Yksi kirjain on tässä sanassa liikaa.

This puts more emphasis on one letter.

In Finnish, word order is more flexible than in English, but it is not random. Moving words changes focus, topic, or emphasis.

For a learner, the original sentence is the safest and most natural version.

Grammatically, on is the 3rd person singular of olla (to be).

• olla = to be
• on = is

But in this type of sentence, English usually translates it as there is:

• Tässä sanassa on... = There is ... in this word

So yes, it is the ordinary verb to be, but in this structure it functions like English there is / there are.

Usually, yes. This sentence would commonly be used when checking a word and noticing that it contains an extra letter.

For example, if someone wrote a word with one unnecessary character, you could say:

• Tässä sanassa on yksi kirjain liikaa.

It is a very natural correction-type sentence.

You can build similar sentences for other errors too:

• Tässä sanassa on yksi kirjain liian vähän. = There is one letter too few in this word.
• Tässä lauseessa on yksi sana liikaa. = There is one word too many in this sentence.

You would say:

• Tässä sanassa on yksi kirjain liian vähän.

Compare:

• liikaa = too much / too many
• liian vähän = too little / too few

So:

• yksi kirjain liikaa = one letter too many
• yksi kirjain liian vähän = one letter too few

This is a very useful pair to learn.