Learn Hardcore Finnish: Koira näkee itsensä peilistä.

In this sentence, Koira näkee itsensä peilistä, context would usually make it clear whether we’re talking about a specific dog (like the dog we were just talking about) or just some dog (a dog).

Also, Koira is capitalized only because it starts the sentence. Finnish does not capitalize nouns like German does.

What verb is näkee, and how is it formed?

The dictionary form of näkee is nähdä (to see).

It is the 3rd person singular present form:

minä näen – I see
sinä näet – you (sg) see
hän / se näkee – he/she/it sees
me näemme – we see
te näette – you (pl) see
he / ne näkevät – they see

Notice:

The stem is näke-.
In näkee, the final -e of the stem plus the personal ending -e create -ee (a long e sound).
The hd in nähdä disappears in most present forms: nähdä → näe-/näke-.

What exactly is itsensä made of, and what does each part mean?

Itsensä is built from:

itse – “self”
stem form itsen-
possessive suffix -sä (here written as -nsä after n)
overall case: genitive/accusative singular (object form)

So you can think of it as:

itsen (of self) + sä (his/her/its) → itsensä
≈ himself / herself / itself as a direct object.

Compare with other persons (all in the same object form):

itseni – myself
itsesi – yourself (sg)
itsensä – himself / herself / itself / themselves
itsemme – ourselves
itsenne – yourselves

In the sentence, itsensä is the object:
Koira (subject) näkee (verb) itsensä (object) peilistä (from the mirror).

Why do we use itsensä and not hänet or sen for “itself”?

Finnish uses itse + possessive suffix as the normal way to say “oneself” (reflexive) when the subject and object are the same.

So:

Koira näkee itsensä = The dog sees itself.
If you said Koira näkee sen, it would mean The dog sees it (some other thing, not itself).
Hänet is the object form of hän (him/her as another person), so Koira näkee hänet = The dog sees him/her.

When the subject and object refer to the same being, Finnish prefers:

minä näen itseni – I see myself
sinä näet itsesi – you see yourself
hän näkee itsensä – he/she/it sees himself/herself/itself

Which grammatical cases appear in this sentence, and what do they do?

The cases are:

Koira – nominative singular
- Subject of the sentence: the dog.
itsensä – genitive/accusative singular
- Functions as a total object: (it)self, fully seen.
- For pronoun-like words with possessive suffixes, the genitive form is used as the accusative (object) in such contexts.
peilistä – elative singular (from the mirror)
- Marks the source or origin of the perception: the dog sees its reflection from the mirror / in the mirror.

So structurally:

Subject (nominative): Koira
Verb: näkee
Object (genitive/accusative): itsensä
Source/location (elative): peilistä

Why is it peilistä and not peilissä or peiliin?

All three forms exist, but they mean different things:

peilissä – in the mirror, on the mirror (inessive: in/inside/at)
peilistä – from the mirror (elative: from the inside/from out of)
peiliin – into the mirror (illative: into, toward the inside)

With perception verbs like nähdä (“see”) and kuulla (“hear”), Finnish very often uses elative for the source of the perception:

nähdä televisiosta – to see (it) on/from TV
lukea lehdestä – to read (it) in/from the newspaper
kuulla radiosta – to hear (it) from the radio
nähdä peilistä – to see (it) from/in the mirror

So peilistä here is the natural idiomatic choice:
Koira näkee itsensä peilistä = The dog sees its reflection (coming) from the mirror.

Would Koira näkee itsensä peilissä be wrong?

It’s not strictly wrong, but it’s less idiomatic for this meaning.

Koira näkee itsensä peilistä is the standard, natural way to say “The dog sees itself in the mirror.”
Koira näkee itsensä peilissä puts more focus on being in/on the mirror as a location, and sounds a bit unusual in this common expression. Some speakers might accept it, but peilistä is by far the default.

A good rule of thumb:

With nähdä/kuulla
- medium (mirror, TV, radio, screen, etc.), prefer elative (-sta/-stä).

How flexible is the word order in Koira näkee itsensä peilistä?

Finnish word order is quite flexible because case endings show who does what. However, changes in order usually change emphasis or information structure.

Neutral, most common:

Koira näkee itsensä peilistä.
→ The dog sees itself in the mirror. (plain statement)

Other possible orders (all grammatically possible):

Koira näkee peilistä itsensä.
– Emphasis can shift slightly to itsensä (what it sees from the mirror).
Itsensä koira näkee peilistä.
– Strong emphasis on itsensä: It is itself that the dog sees from the mirror (contrast: not something else).
Peilistä koira näkee itsensä.
– Emphasis on peilistä: From the mirror the dog sees itself (e.g., not from a window).

The basic meaning (subject = dog, object = itself, source = mirror) remains the same because of the case endings, but word order lets you highlight different parts.

How would this sentence look with different persons: “I see myself”, “you see yourself”, etc.?

Using nähdä and itse + possessive suffix, we get:

Minä näen itseni peilistä. – I see myself in the mirror.
Sinä näet itsesi peilistä. – You (sg) see yourself in the mirror.
Hän näkee itsensä peilistä. – He/She sees himself/herself in the mirror.
Me näemme itsemme peilistä. – We see ourselves in the mirror.
Te näette itsenne peilistä. – You (pl) see yourselves in the mirror.
He näkevät itsensä peilistä. – They see themselves in the mirror.

Reflexive forms of itse here:

1st sg: itseni
2nd sg: itsesi
3rd sg/pl: itsensä
1st pl: itsemme
2nd pl: itsenne

The structure stays the same; only the subject, verb form, and reflexive pronoun change.

How would you say “The dog sees another dog in the mirror” to contrast with “sees itself”?

To clearly say that the dog sees some other dog, not itself, you avoid the reflexive itsensä and use a normal noun phrase:

Koira näkee toisen koiran peilistä.
– The dog sees another dog in the mirror.

Breakdown:

Koira – the dog (subject)
näkee – sees
toisen koiran – another dog (object: “the other dog”)
peilistä – in/from the mirror

Comparing:

Koira näkee itsensä peilistä. – The dog sees itself in the mirror.
Koira näkee toisen koiran peilistä. – The dog sees another dog in the mirror.

Why is it itsensä and not the partitive form itseään?

Finnish objects can be in:

Total object form (genitive/accusative) → the action is seen as whole, complete.
Partitive form → the action is partial, ongoing, or otherwise “not complete”.

Here we have:

itsensä – genitive/accusative (total object)
itseään – partitive

In Koira näkee itsensä peilistä, the dog sees its whole self in a single, complete act of seeing, so the total object itsensä is natural.

Partitive itseään might appear in other constructions, for example:

Koira katseli itseään pitkään peilistä.
– The dog watched/was looking at itself in the mirror for a long time.
(ongoing activity → partitive itseään is common)

How would you say “The dogs see themselves in the mirror”?

For a plural subject, you make the subject and verb plural, but the reflexive form itsensä stays the same for 3rd person plural:

Koirat näkevät itsensä peilistä.
– The dogs see themselves in the mirror.

Breakdown:

Koirat – dogs (nominative plural, subject)
näkevät – they see (3rd person plural of nähdä)
itsensä – themselves (3rd person reflexive, used for both singular himself/herself/itself and plural themselves)
peilistä – in/from the mirror

Context (plural koirat, plural verb näkevät) tells you that itsensä here means themselves, not just a single self.