Learn Hardcore Finnish: Ergonomia on tärkeä myös kotona, jos työskentelee monta tuntia keittiön pöydän ääressä. - Ergonomics is important also at home if you work many hours at the kitchen table.

sitting at a table
- pöydän ääressä = at the table
working at a desk
- kirjoituspöydän ääressä = at the desk
being by some vertical surface (often with working/doing something there)
- ikkunan ääressä = by the window (e.g. sitting there)

In your sentence:

keittiön pöydän ääressä = at the kitchen table

Comparison:

päällä = on top of
- pöydän päällä = on the table (on its surface)
luona = at someone’s place / with someone / by (a person or place)
- ystävän luona = at a friend’s place
- lääkärin luona = at the doctor’s (office)

So ääressä emphasizes that you are sitting/being at the side of something (especially a table/desk), not on top of it or at someone’s place.

Why is it työskentelee (3rd person) and not työskentelen or työskentelet?

Työskentelee is 3rd person singular, but here it’s not talking about he/she specifically. It’s an impersonal / generic “you / one / people”:

jos työskentelee monta tuntia…
≈ if you work / if one works / if people work many hours…

Finnish often uses 3rd person singular without a subject to talk about:

people in general
a typical or habitual situation

Other examples:

Kun istuu pitkään, selkä väsyy.
When you sit for a long time, your back gets tired.
Autolla ajaessa pitää olla varovainen.
When driving a car, you have to be careful.

So the sentence does not literally mean “if he/she works many hours…”, but “if you/one works many hours… in general”.

Could I say jos sinä työskentelet monta tuntia… instead? Does it change the meaning?

Yes, you can say:

Ergonomia on tärkeä myös kotona, jos sinä työskentelet monta tuntia keittiön pöydän ääressä.

Grammatically it’s correct, and the meaning is similar, but the tone is different:

jos työskentelee
= neutral, general statement about “anyone”
jos sinä työskentelet
= addressed directly to “you”; sounds a bit more personal, even slightly emphatic (especially with sinä explicitly stated).

In everyday speech, Finns often prefer the impersonal form for general advice:

Jos työskentelee kotona, ergonomia on tärkeä.
If you work at home, ergonomics is important.

So your version is fine, but feels more like speaking directly to one specific person.

Why do we say monta tuntia, and why is tuntia in that form?

Monta means “many (of something)” and it requires the partitive case after it.

monta tuntia
- mon-ta = many (count)
- tunti-a = hour in partitive singular
  → literally: many (units of) hour

This is a fixed pattern:

monta tuntia – many hours
monta kirjaa – many books
monta kertaa – many times

Why partitive singular (tuntia) and not plural?

Finnish often uses partitive singular after words like monta and paljon:

monta tuntia / paljon aikaa
monta taloa / paljon taloja

You can also say:

monia tunteja
(monia = partitive plural of moni)

This is also correct, a bit more formal or emphatic, but monta tuntia is more common and very natural.

What are the roles of the cases in keittiön pöydän ääressä?

Breakdown:

keittiön
- from keittiö (kitchen)
- genitive: “of the kitchen”
pöydän
- from pöytä (table)
- genitive: “of the table”
ääressä
- postposition: “at / by / at the edge of”

Structure:

keittiön pöytä = the kitchen’s table → kitchen table
keittiön pöydän ääressä
= at the kitchen table

The genitives chain together to build a complex noun phrase:

[keittiön] [pöydän] ääressä
“at [the table] [of the kitchen]”

Why is it kotona and not kotona, kotiin, or kodissa? How do these differ?

All of these come from koti (home), but with different cases/meanings:

kotona = “at home” (internal location, static)
- Olen kotona. – I am at home.
kotiin = “(to) home” (movement towards)
- Menen kotiin. – I’m going home.
kodissa = “in (a) home/house” (more literal, inside a home)
- Asun vanhassa kodissa. – I live in an old home/house.

In your sentence, we talk about the state of being at home, not going there or being inside some house as an object, so:

Ergonomia on tärkeä myös kotona…
= Ergonomics is important at home too…

Using kotona is the normal, idiomatic way.

Why Ergonomia on tärkeä and not Ergonomia on tärkeää? Are both correct?

Both tärkeä and tärkeää are possible, but there is a nuance.

Ergonomia on tärkeä.
- tärkeä = nominative singular adjective
- Treats ergonomia as a kind of “thing” or field that is important.
- Feels a bit more concrete / specific:
  This aspect called ergonomics is an important thing.
Ergonomia on tärkeää.
- tärkeää = partitive, “neuter”‑like predicative
- Common with abstract nouns when talking generally:
  Ergonomics (as a concept in general) is important.

In everyday speech:

You’ll often hear “Ergonomia on tärkeää.” as a general statement.
The given sentence “Ergonomia on tärkeä myös kotona…” is also used, especially when you’re sort of personifying or highlighting ergonomics as a specific, concrete factor in that home situation.

So: both are grammatical; the difference is subtle, and using tärkeää is always safe with an abstract noun like ergonomia.

What does myös do here, and could it be placed somewhere else in the sentence?

Myös means “also / too”.

In Ergonomia on tärkeä myös kotona…, it emphasizes that:

ergonomics is important at home too, not only in the office, etc.

Word order with myös is relatively flexible, with small differences in emphasis:

Ergonomia on tärkeä myös kotona.
→ neutral, focuses on home as an additional place.
Myös kotona ergonomia on tärkeä.
→ emphasizes “also at home” at the start.
Ergonomia on myös tärkeä kotona.
→ emphasizes that ergonomics too is important at home (along with other things).
Kotona ergonomia on myös tärkeä.
→ contrastive: at home, ergonomics is also important (maybe plus something else).

Your version is perfectly natural and common.

What’s the difference between jos and kun here? Could I say kun työskentelee monta tuntia…?

Both jos and kun can be translated as “if / when”, but they differ:

jos = if, conditional, uncertain
- jos työskentelee monta tuntia…
  → if you work many hours… (in the case that you do)
kun = when, time reference, something that actually happens or is expected
- kun työskentelee monta tuntia…
  → when you work many hours (as you in fact do / will)

You can say:

Ergonomia on tärkeä myös kotona, kun työskentelee monta tuntia keittiön pöydän ääressä.

This suggests that working many hours at the kitchen table is a real, typical situation, not just a hypothetical one.

With jos, it’s a bit more like general advice applying in that case.

Why is it keittiön pöytä (kitchen’s table) and not just one compound noun like keittiöpöytä?

Both exist, but they’re not identical:

keittiön pöytä
- literally “the kitchen’s table”
- any table that belongs to / is in the kitchen
keittiöpöytä
- compound noun, “kitchen table” as a type of table
- a table designed for use in a kitchen

In your sentence, keittiön pöydän ääressä:

is about an actual specific table that is in your kitchen.
sounds very natural when talking about your real home situation.

You could say keittiöpöydän ääressä, and it wouldn’t be wrong; it just sounds a bit more like talking about the kind/type of table, not necessarily “the table of this kitchen” in a concrete home.

Why not say pöydän päällä instead of pöydän ääressä?

Because the meaning would change:

pöydän ääressä = at the table (sitting/standing next to it, using it)
pöydän päällä = on top of the table (on its surface)

Työskentelee monta tuntia keittiön pöydän päällä would literally mean:

works for many hours on top of the kitchen table (like physically on the surface—standing or lying there).

So for normal “sitting at the table and working”, ääressä is the correct and idiomatic choice.

Can the jos‑clause come first? For example: Jos työskentelee monta tuntia…, ergonomia on tärkeä myös kotona.

Yes, absolutely. Both orders are natural:

Ergonomia on tärkeä myös kotona, jos työskentelee monta tuntia keittiön pöydän ääressä.
Jos työskentelee monta tuntia keittiön pöydän ääressä, ergonomia on tärkeä myös kotona.

The meaning is the same. Starting with the jos‑clause is even very typical in Finnish, especially in written advice or instructions, because it sets the condition/situation first, then the conclusion.