Learn Hardcore Finnish: Kynttilä palaa hiljaa, kun perhe syö iltapalaa. - The candle burns quietly when the family eats an evening snack.

palaa = to burn / to be on fire (something burns by itself)
- Kynttilä palaa. = The candle is burning.
polttaa = to burn something (you cause something to burn)
- Poltan kynttilää. = I am burning a candle.

In your sentence, the candle is just burning by itself, so the correct verb is palaa, not polttaa.

What exactly does hiljaa mean here, and why not hiljaisesti?

Hiljaa is an adverb meaning quietly / softly / silently. It describes how the candle is burning.

Kynttilä palaa hiljaa.
→ The candle burns quietly/softly.

You can also say hiljaisesti, but:

hiljaa is more common and natural in everyday language in expressions like this.
hiljaisesti can sound a bit more formal or literary, or sometimes slightly more “careful” or “deliberate”.

Both are grammatically correct, but hiljaa is the default choice here.

Why is there a comma before kun? In English we often skip commas with “when”.

In Finnish, the rule is stricter than in English:

A main clause and a subordinate clause are separated by a comma, always, regardless of the order.

Here:

Main clause: Kynttilä palaa hiljaa
Subordinate clause: kun perhe syö iltapalaa

So you must write:

Kynttilä palaa hiljaa, kun perhe syö iltapalaa.
Kun perhe syö iltapalaa, kynttilä palaa hiljaa.

The comma is obligatory in both versions.

What does kun mean here exactly – “when” or “while”?

Kun is a conjunction that can mean:

when (time)
while (simultaneous time)
sometimes because (causal), depending on context

In this sentence, the meaning is temporal and simultaneous:

Kynttilä palaa hiljaa, kun perhe syö iltapalaa.
→ The candle is burning quietly *while the family is eating supper.
(also natural to translate as *when the family is eating supper.)

So here kun is best understood as when/while.

Why is it perhe syö, not perhe syövät, since “family” is many people?

Grammatically, perhe (family) is singular in Finnish:

perhe = one family (even though it contains multiple people)
Therefore the verb agrees in the singular: perhe syö

So:

Perhe syö iltapalaa. = The family is eating supper.

In spoken Finnish, you might hear forms like perhe syövät, treating “family” more like a plural group, but in standard written Finnish, the correct form is perhe syö.

What is iltapala, and why is it iltapalaa here?

Vocabulary first:

ilta = evening
pala = piece, morsel
iltapala (compound noun) = a light evening snack / light evening meal

Case and form:

iltapala is the nominative form (dictionary form).
iltapalaa is the partitive singular.

The ending -a here marks the partitive case:

iltapala → iltapalaa

So syö iltapalaa literally means eats (some) evening snack, expressing the meal as an ongoing activity or an indefinite amount.

Why is the object in the partitive: syö iltapalaa instead of syö iltapalan?

Finnish chooses object case based on aspect and completeness:

Partitive object (iltapalaa)
- Often used for ongoing, incomplete, or indefinite amount.
- Perhe syö iltapalaa.
  → The family is (in the process of) eating supper / having an evening snack.
Total object (genitive: iltapalan)
- Used when the action is seen as complete or the object is treated as a whole, bounded thing.
- Perhe syö iltapalan.
  → The family (will) eat/finish their evening snack (entirely).

In neutral descriptions of what people are eating at a given time, Finnish very often uses the partitive:

Juon kahvia. = I am drinking (some) coffee.
Syömme lounasta. = We are having lunch.
Perhe syö iltapalaa. = The family is having an evening snack.

Is the Finnish present tense here more like English “eats” or “is eating”?

Finnish has one present tense, and context decides whether English should use simple present or present continuous:

Kynttilä palaa hiljaa, kun perhe syö iltapalaa.

This can mean:

A general/habitual situation:
- The candle burns quietly when the family eats supper.
A situation happening right now:
- The candle is burning quietly while the family is eating supper.

Both interpretations are possible; English must choose between “eats” and “is eating”, but Finnish doesn’t make that grammatical distinction.

Could the word order be changed, for example Hiljaa palaa kynttilä, and would it change the meaning?

Yes, Finnish allows flexible word order, but it changes emphasis, not the basic meaning.

Kynttilä palaa hiljaa, kun perhe syö iltapalaa.
→ neutral: subject–verb–adverb; focus not specially marked.

Possible variants of the main clause:

Hiljaa kynttilä palaa, kun perhe syö iltapalaa.
→ Emphasis more on hiljaa (“quietly is how the candle is burning”).
Kynttilä hiljaa palaa, kun perhe syö iltapalaa.
→ Also gives a slightly poetic or stylistic twist, foregrounding hiljaa.

All are grammatically correct; the original is the most neutral and natural in standard prose.

Can I say Kun perhe syö iltapalaa, kynttilä palaa hiljaa instead?

Yes, absolutely. That’s also completely correct:

Kun perhe syö iltapalaa, kynttilä palaa hiljaa.

The meaning is the same; you’ve just fronted the time clause:

First: when the family is eating supper,
then: the candle is burning quietly.

Only the order and rhythm of the sentence change; the content and grammar remain the same (and the comma is still required).