Learn Hardcore Finnish: Laitan puhelimen pois, ettei se häiritse minua yöllä. - I put the phone away so that it doesn’t disturb me at night.

The context (the rest of the sentence, especially yöllä, “at night”) tells us that this is about a future time, even though the verb form is present.

Why is it puhelimen and not puhelin or puhelinta?

Puhelimen is the total object form of puhelin.

puhelin = nominative (dictionary form)
puhelimen = genitive/accusative (used as total object)
puhelinta = partitive (often used for incomplete/ongoing actions, or with some verbs)

Here, laitan puhelimen pois describes a complete, bounded action: you are putting the whole phone away / turning it off completely. That’s why Finnish uses the total object:

Laitan puhelimen pois. = I’ll put the phone away (completely).
Compare: Etsin puhelinta. = I’m looking for (my) phone. (Ongoing, not completed action → partitive)

What does pois add? Why not just laitan puhelimen?

The verb laittaa means roughly “to put / to place”, but often needs an adverb or complement:

laittaa pöydälle = to put (something) on the table
laittaa takaisin = to put (it) back
laittaa pois = to put away, to put aside, to turn off (for devices)

In this sentence:

laitan puhelimen = I put the phone (somewhere) – sounds incomplete without a location or adverb.
laitan puhelimen pois = I put the phone away / I turn off the phone.

So pois expresses the idea of “away / off / out of use”, especially with devices.

What is ettei exactly, and how does it differ from että ei?

Ettei is a contracted form of että ei:

että = that / so that
ei = not

So ettei literally means “so that not / in order that not”, and it introduces a negative purpose clause:

Laitan puhelimen pois, ettei se häiritse minua yöllä.
= I’ll put the phone away so that it doesn’t disturb me at night.

You could say että ei se häiritse, but in standard Finnish, ettei is the normal, smooth way to express this. Usually:

että
- ei → ettei
jotta
- ei → jottei

Both ettei and että ei are grammatically understandable, but ettei is the natural, idiomatic form here.

Why is there a comma before ettei?

In Finnish, a comma is normally used before most subordinate clauses, including those introduced by että / ettei / koska / jos, etc.

Laitan puhelimen pois, ettei se häiritse minua yöllä.
Main clause: Laitan puhelimen pois
Subordinate clause: ettei se häiritse minua yöllä

So the comma is required by Finnish punctuation rules, not optional style as often in English.

Why is it se häiritse and not sitä häiritse or se häiritsee?

Break it down:

se
- This is the subject pronoun: “it” (referring to puhelin).
- Since se is the subject, it’s in the nominative form.
häiritse
- This is the negative form of the verb häiritä (to disturb) in the 3rd person singular with ei:
  - (se) häiritsee = it disturbs
  - (se) ei häiritse = it does not disturb
In the sentence, häiritse is still grammatically tied to a negation (through ettei), so it keeps the negative stem form:
- ettei se häiritse = so that it does not disturb
Why not sitä?
- sitä is an object form (partitive of se).
- But in this clause, se is clearly the subject (the thing that does the disturbing), so nominative se is correct.

Why is it minua and not minut or minä?

Minua is the partitive form of minä.

The verb häiritä (“to disturb, bother”) normally takes its object in the partitive:

Se häiritsee minua. = It bothers me.
Melua kuului, ja se häiritsi minua. = There was noise and it disturbed me.

So:

minä = I (subject form)
minut = me (accusative, total object)
minua = me (partitive object, used with many verbs including häiritä)

Because häiritä wants a partitive object, minua is the only natural choice here.

Why is it yöllä and not something like yönä or just yö?

Yöllä is the adessive form of yö (night) and it means “at night” / “during the night”.

yö = night (basic form)
yöllä = at night
yönä (essive) = as a night / in the role of night (rare and different meaning)

In time expressions, -lla/-llä (adessive) is very common:

päivällä = in the daytime / during the day
illalla = in the evening
yöllä = at night

So minua yöllä = me at night → together: häiritä minua yöllä = to disturb me at night.

Could you drop se and just say “…ettei häiritse minua yöllä”?

In this particular sentence, you usually keep the pronoun:

Laitan puhelimen pois, ettei se häiritse minua yöllä.

You might hear …ettei häiritse minua yöllä in casual speech if the subject is very obvious from context, but in normal, clear standard Finnish, the subject se is kept.

Without se, the clause becomes a bit vague: “so that doesn’t disturb me at night” – what doesn’t disturb me? Finnish doesn’t drop subjects as freely as some other languages when they are pronouns other than minä/sinä/me/te.

Is there a difference between pois and poissa here?

Yes, they are different:

pois = away / off (movement, change of state)
- Laitan puhelimen pois. = I put the phone away / turn it off.
- Mene pois! = Go away!
poissa = away / absent (state, result)
- Puhelin on poissa. = The phone is gone / not here.
- Hän on poissa töistä. = He/she is away from work.

In your sentence you are causing the phone to become away/off, so pois (direction/change) is correct, not poissa (state).

Are there other natural ways to say the same thing in Finnish?

Yes, several options with slightly different nuances:

Sammutan puhelimen, ettei se häiritse minua yöllä.
= I’ll turn off the phone so it doesn’t disturb me at night.
(sammuttaa focuses on turning the device off.)
Laitan puhelimen äänettömälle, ettei se häiritse minua yöllä.
= I’ll put the phone on silent so it doesn’t disturb me at night.
Laitan puhelimen lentokonetilaan, ettei se häiritse minua yöllä.
= I’ll put the phone in airplane mode so it doesn’t disturb me at night.

The original laitan puhelimen pois is a bit more general: it can mean putting it out of reach or turning it off; context decides the exact nuance.