Learn Hardcore Finnish: Otan yhden askeleen taaksepäin, koska katu on liukas. - I take one step back because the street is slippery.

Finnish usually drops the subject pronoun because the verb ending already shows the person. Otan has the -n ending, which marks 1st person singular (I). You can add minä for emphasis/contrast (e.g., Minä otan…, “I will take…”), but it’s not required.

What exactly is otan grammatically?

Otan is the present tense, 1st person singular form of the verb ottaa (to take).
So literally it’s I take, but in Finnish ottaa is also used in everyday movement expressions like ottaa askel = “take a step.”

Why does it say yhden askeleen instead of yksi askel?

Because in this sentence the phrase is the object of the verb (I take…), and it’s treated as a total / complete object (“one whole step”). Total objects often appear in the genitive singular in the present tense.

Dictionary/basic form: yksi askel = “one step”
Object here: (otan) yhden askeleen = “(I take) one step” (completed/whole)

If you used a partial object (partitive), it would suggest an incomplete/ongoing amount, e.g. otan askelta would sound like “I’m taking a step (in progress)” or “some stepping,” depending on context.

Why do both words change: yksi → yhden and askel → askeleen?

They change because the whole noun phrase is in the genitive singular as a total object:

yksi (one) → yhden (genitive/“of one” form used here)
askel (step) → askeleen (genitive singular)

With one, the noun is singular (unlike numbers 2+ where Finnish typically uses partitive singular: kaksi askelta = “two steps”).

Is yhden askeleen an accusative?

Finnish doesn’t have a separate accusative form for most nouns; the “accusative object” meaning is often shown by:

genitive singular (like askeleen) in many positive present/past sentences, or
nominative (especially with imperatives and some passives), or
partitive for partial/unfinished objects.

So in function it’s an accusative-type object, but in form it’s genitive singular.

What is taaksepäin—is it a case form, a postposition, or just an adverb?

Taaksepäin functions as an adverb meaning back / backwards.

It’s built from:

taakse = “to the back” (a directional form)
päin = “towards / in the direction of”

Together, taaksepäin emphasizes direction: “backwards / towards the back.”

Could I say Otan yhden askeleen taakse instead of taaksepäin?

Often yes, and it would still mean “I take one step back.”
A rough nuance:

taakse = “to the back” (destination/direction)
taaksepäin = “backwards” (direction/manner, often more clearly “backwards”)

In many everyday contexts they overlap, but taaksepäin can feel a bit more like “backwards” as a movement direction.

Why is there a comma before koska?

In Finnish, a subordinate clause introduced by koska (“because”) is typically separated from the main clause with a comma:

Otan…, koska…
This is standard punctuation when the koska-clause follows the main clause.

Can the sentence start with the koska clause?

Yes. Finnish allows flexible word order. You can say:

Koska katu on liukas, otan yhden askeleen taaksepäin.

Meaning stays the same, but starting with Koska… puts the reason first and can feel slightly more explanatory.

Why is it katu on liukas and not something like katu on liukasta?

Because katu is a specific subject (the street), and the adjective used as a predicative normally agrees in nominative singular:

katu (nom. sg.) + on
- liukas (nom. sg.)

Finnish uses an impersonal structure with partitive to express “it’s slippery (in general)”:

On liukasta. = “It’s slippery.” (general conditions) Or with a location plural:
Kaduilla on liukasta. = “It’s slippery on the streets.”