Learn Hardcore Finnish: Minä nostan lautasen pöydältä.

Minä – I (1st person singular pronoun)
nostan – I lift / I raise / I pick up (present tense of nostaa)
lautasen – the plate as a total object (genitive/accusative form of lautanen)
pöydältä – from the table / off the table (ablative case of pöytä, “from a surface”)

So literally: I lift the plate from/off the table.

Is Minä necessary here, or can I leave it out?

You can usually leave Minä out:

Minä nostan lautasen pöydältä.
Nostan lautasen pöydältä.

Both mean I lift the plate from the table.

In Finnish, the personal ending on the verb (-n in nostan) already shows the subject is I, so the pronoun is often omitted unless you:

want to emphasize I specifically:
- Minä nostan lautasen pöydältä, en sinä. – I will lift the plate, not you.
are speaking very clearly or formally (e.g. in a textbook example).

In everyday speech you will hear Nostan lautasen pöydältä more often than Minä nostan….

What verb form is nostan, and how is it formed from nostaa?

Nostan is:

present tense
1st person singular
indicative mood
of the verb nostaa (to lift, to raise).

For a regular type 1 verb like nostaa, the present tense is formed like this:

infinitive: nostaa
verb stem: nosta-
add personal endings:
- nostan – I lift
- nostat – you (sg) lift
- nostaa – he/she lifts
- nostamme – we lift
- nostatte – you (pl) lift
- nostavat – they lift

Nostan can translate to both I lift / I am lifting / I will lift, depending on context. Finnish does not have a separate continuous or future tense; the simple present covers these meanings.

Why is it lautasen and not lautanen? What case is that?

Lautasen is the genitive/accusative form of lautanen (plate). Here it functions as a total object.

basic form (nominative): lautanen – plate
genitive/accusative (total object): lautasen – the plate (as a whole)

With a normally completed, bounded action (you fully lift the plate off the table), a singular object in Finnish usually appears in the genitive/accusative (-n) form:

Nostan lautasen pöydältä. – I lift the plate (completely).

So lautasen shows that we mean the entire plate as the completed object of the action.

Would Minä nostan lautanen pöydältä be correct?

No, that is ungrammatical.

The object here must be in the genitive/accusative form because:

it is singular
the action is completed/total
the verb is transitive

So you need:

Minä nostan lautasen pöydältä. ✅
not
✗ Minä nostan lautanen pöydältä.

Lautanen (nominative) would be correct as a subject, not as this kind of object:

Lautanen putoaa pöydältä. – The plate falls from the table. (Here lautanen is the subject.)

When would I use a partitive object like lautasta instead of lautasen?

With nostaa, the partitive lautasta is unusual but possible in some special meanings. In general:

Genitive/accusative (lautasen) – total, completed, whole object
- Nostan lautasen pöydältä. – I lift the entire plate off the table.
Partitive (lautasta) – incomplete, ongoing, unbounded, or “some (of)”
Possible but a bit contrived here, e.g.:
- Nostan lautasta hitaasti. – I am (in the middle of) lifting the plate, not necessarily finishing.
- Nostelin lautasta koko ajan. – I kept (repeatedly) lifting the plate (imperfective/repeated nuance).

With verbs where “some of / an indefinite amount” makes more sense, the partitive is very common:

Juon vettä. – I drink (some) water.
Syön leipää. – I eat (some) bread.

With nostaa + lautanen, the normal, natural form in your sentence is lautasen.

What does the ending -ltä in pöydältä mean, and how is it different from pöydällä and pöydälle?

Pöydältä is the ablative case: it means from a surface / off a surface.

For pöytä (table), the “outer local” cases are:

pöydällä (adessive, -lla/-llä) – on the table / at the table
- Lautanen on pöydällä. – The plate is on the table.
pöydälle (allative, -lle) – onto the table / to the table
- Laitan lautasen pöydälle. – I put the plate onto the table.
pöydältä (ablative, -lta/-ltä) – from the table / off the table
- Nostan lautasen pöydältä. – I lift the plate off the table.

So -llä / -lle / -ltä indicate on/at, onto/to, and from/off a surface or an external location.

Why is it pöydältä and not something like pöytästä? What’s going on with the stem change?

The basic form is pöytä (table), but in many case forms the stem becomes pöydä-:

pöydällä – on the table
pöydälle – onto the table
pöydältä – from the table
pöydän – of the table / the table’s

This -d- is a regular stem change in Finnish: pöytä → pöydä- before many endings.

As for pöytästä:

pöydästä (inner case -sta/-stä) would mean from inside the table (from its interior), which is usually nonsensical for a plate.
For something sitting on the surface of the table, you normally use the outer cases (-lla / -lta / -lle), hence pöydältä.

What question does pöydältä answer, grammatically speaking?

Pöydältä answers the question “from where?”:

Mistä? – from where?
- Mistä nostat lautasen? – From where do you lift the plate?
- (Minä) nostan lautasen pöydältä. – (I) lift the plate from the table.

More specifically, with outer local cases:

Miltä (pinnalta)? – from which surface?
- Miltä nostat lautasen? – From which (surface) do you lift the plate?
- Pöydältä. – From the table.

So pöydältä is an adverbial of place, telling you where the movement starts.

How flexible is the word order in Minä nostan lautasen pöydältä?

Finnish word order is more flexible than English. All of these are grammatically correct, but with slightly different emphasis:

Minä nostan lautasen pöydältä. – neutral; slight emphasis on Minä if pronounced strongly.
Nostan lautasen pöydältä. – neutral, natural everyday word order.
Lautasen nostan pöydältä. – emphasizes the plate (not something else).
Pöydältä nostan lautasen. – emphasizes from the table (as opposed to from somewhere else).

Basic neutral order is usually Subject – Verb – Object – Place/Time:

(Minä) nostan lautasen pöydältä.

Moving elements to the front tends to highlight or contrast them.

How would this sentence normally sound in casual spoken Finnish?

In everyday colloquial Finnish, you will often hear:

Mä nostan lautasen pöydältä. – using mä instead of minä
or simply
Nostan lautasen pöydältä. – dropping the pronoun.

Other very colloquial variants might shorten vowels or soften consonants in fast speech, but the main “textbook vs spoken” difference is:

minä → mä (I)
sinä → sä (you)

The rest of the sentence (nostan lautasen pöydältä) stays the same.

Could I use otan instead of nostan? What is the difference in meaning?

Yes, you can say:

Minä otan lautasen pöydältä.

Otan is from ottaa (to take), so this means I take the plate from the table.

Nuances:

nostaa – focuses on the lifting/raising motion.
ottaa – focuses on taking/grabbing/choosing something, not necessarily emphasizing the upward motion.

In many everyday contexts:

Otan lautasen pöydältä. – I take the plate from the table.
is at least as common, and often more idiomatic, than
Nostan lautasen pöydältä. – I lift the plate from the table.

The nostaa version sounds slightly more physical or descriptive of the movement itself.

How would the sentence change if there were several plates?

For multiple plates, you have two common options, depending on meaning:

All the plates (total objects, plural nominative):
- Nostan lautaset pöydältä.
  – I lift the plates (all of them) from the table.
Some plates / plates in an unbounded sense (partitive plural):
- Nostan lautasia pöydältä.
  – I lift (some) plates from the table / I’m lifting plates (not specifying how many or whether it’s all of them).

So,

lautasen – the (one) plate, total
lautaset – the plates, total (all)
lautasia – plates in partitive plural: some/unspecified/ongoing amount.