suyaki ga owatta.

It is read:

すやき が おわった。

• 素焼き（すやき）
• が
• 終わった（おわった）

Because 終わる is an intransitive verb.

In Japanese, with intransitive verbs, the thing that undergoes the change is often marked with が. Here, 素焼き is the thing that ended, so it takes が:

• 素焼きが終わった。 = The bisque firing ended / is finished.

If you used a transitive verb instead, you would usually use を:

• 素焼きを終えた。 = (Someone) finished the bisque firing.

So the sentence you have focuses on the event itself being over, not on a person actively finishing it.

This is a very common question.

• 終わる = to end / to be over
  → intransitive
• 終える = to finish something
  → transitive

So:

• 素焼きが終わった。
  = The bisque firing ended / is over.

• 素焼きを終えた。
  = I/We finished the bisque firing.

The sentence with 終わった sounds more like describing a state or event. The sentence with 終えた sounds more like emphasizing the actor who completed it.

Grammatically, it means it ended / it was finished rather than explicitly someone finished it.

Japanese often leaves the human subject unstated, and English translations may sometimes sound active, but the grammar here is still based on 終わる, not 終える.

So the most direct sense is:

• The bisque firing ended.
• The bisque firing is finished.

In context, English might naturally say We finished the bisque firing, but that is a looser translation, not the literal grammatical structure.

終わった is the plain past form of 終わる.

• dictionary form: 終わる
• past plain form: 終わった

In English, depending on context, this can be translated as:

• ended
• was over
• has finished
• is finished

Japanese past forms often cover both a simple past sense and a present-result sense, depending on context.

It is in the plain style, which is less formal than polite speech.

• 素焼きが終わった。 = plain
• 素焼きが終わりました。 = polite

The plain form is very common in:

• casual conversation
• narration
• diary-style writing
• internal thoughts
• technical or matter-of-fact statements in the right context

So it is not rude by itself; it is just not in the polite ます style.

In this sentence, 素焼き most likely refers to bisque firing or the first firing of pottery before glazing.

That is important because 素焼き can have different meanings depending on context, such as:

• unglazed pottery
• plain grilling / roasting
• bisque firing in ceramics

Since the sentence says 素焼きが終わった, it sounds very natural in a pottery context as The bisque firing is finished.

Japanese often omits things that are understood from context.

In English, you usually need a subject:

• It ended
• We finished it

In Japanese, if the topic is already clear, you can simply say:

• 素焼きが終わった。

That is a complete sentence. The listener is expected to understand what is being talked about from the situation.

Yes, 素焼きは終わった。 is possible, but it has a slightly different feel.

• 素焼きが終わった。
  Neutral: The bisque firing ended.
• 素焼きは終わった。
  Adds a contrastive or topical nuance: As for the bisque firing, that’s finished (maybe implying something else is not finished yet).

So が is the more straightforward choice if you are simply reporting that the firing ended.

Yes, very often it does.

Even though 終わった is grammatically past tense, Japanese often uses the past form to express that something has been completed and is now in the state of being over.

So in natural English, this could be:

• The bisque firing ended.
• The bisque firing is over.
• The bisque firing is finished.

Which one sounds best depends on context.

Yes, absolutely.

Japanese often uses short, context-dependent sentences, especially when:

• reporting progress
• making observations
• giving updates

So 素焼きが終わった。 can naturally stand alone as:

• an observation
• a status update
• a note in a pottery studio
• part of a conversation

It is short, natural, and complete.