zitai ga kawarimasita.

It is read:

じたい が かわりました。

Breakdown:

• 事態（じたい） = situation, state of affairs, development
• が = subject marker
• 変わりました（かわりました） = changed / has changed

The verb comes from the dictionary form 変わる（かわる）.

事態 is a bit more serious or formal than a simple situation in everyday English.

It often refers to:

• a state of affairs
• a turn of events
• a development in a matter
• a situation, especially one with some importance or seriousness

So 事態が変わりました can sound more formal or weighty than something like:

• 状況が変わりました = the situation/circumstances changed

Very roughly:

• 事態 = the overall state of events, often in a significant matter
• 状況 = circumstances, conditions, situation more generally

Because 変わる is an intransitive verb.

That means the thing marked by が is the thing that undergoes the change:

• 事態が変わりました = the situation changed

You do not use を with 変わる.

Compare:

• 変わる = to change, to become different (something changes)
• 変える = to change something (someone changes something)

So:

• 事態が変わりました = the situation changed
• 彼が事態を変えました = he changed the situation

Yes, you can, but the nuance changes.

• 事態が変わりました simply presents the situation as the thing that changed.
• 事態は変わりました makes 事態 the topic, often with a contrastive or topical feeling, like:
  • As for the situation, it changed
  • The situation, at least, has changed

So if you are just neutrally reporting a change, が is very natural.

If you want to contrast it with something else, は may fit better:

• 人の気持ちは変わっていませんが、事態は変わりました。
  • People’s feelings have not changed, but the situation has.

The dictionary form is 変わる（かわる）.

This sentence uses the polite past form:

• dictionary: 変わる
• polite non-past: 変わります
• polite past: 変わりました

So 変わりました is simply the polite past form of 変わる.

Because 変わる and 変える are a very common intransitive/transitive pair.

• 変わる = something changes
• 変える = someone changes something

In your sentence, the situation itself is changing, so Japanese uses 変わる:

• 事態が変わりました = the situation changed

If a person actively changed the situation, you would use 変える:

• 彼が事態を変えました = he changed the situation

Japanese past tense often covers both:

• simple past: changed
• present perfect-like meaning: has changed

So 変わりました can mean:

• changed
• has changed

In this sentence, it usually means the change has already happened, and the new situation is now different.

That is very natural Japanese usage. You do not need a special separate form just to express has changed here.

It is polite, but not extremely formal.

Why:

• 変わりました uses the ます form, which is polite.
• 事態 itself sounds somewhat formal or serious.

So the whole sentence feels suitable for:

• news
• business
• reports
• serious conversation
• formal or semi-formal speech

A casual version would be:

• 事態が変わった。

Yes, Japanese often omits things that are clear from context.

For example, if everyone already knows what is being discussed, someone might simply say:

• 変わりました。 = It changed / Things changed.

But 事態 is included here because the speaker wants to clearly identify what changed:

• the situation
• the state of affairs
• the development

Japanese includes nouns like this when clarity or emphasis is needed.

変わる is a godan verb, not an ichidan verb.

Even though it ends in る, it does not behave like verbs such as 食べる.

Conjugation:

• dictionary: 変わる
• polite: 変わります
• past plain: 変わった
• past polite: 変わりました
• te-form: 変わって

This is important because learners sometimes assume all -る verbs are ichidan, but 変わる is not.

Yes, it is natural, especially in contexts where some important development has occurred.

It can sound like:

• a report
• an update
• a serious announcement
• a turning point in events

For example:

• in a business meeting
• during a crisis
• in a detective story
• in the news

Because 事態 is a fairly weighty word, the sentence can feel more dramatic or official than a plain everyday statement.

A useful basic pronunciation guide is:

• じたい = usually pronounced smoothly as ji-tai
• かわりました = ka-wa-ri-ma-shi-ta

Main things to watch:

• Do not pronounce 事態 like English gee-tie; it is ji-tai
• The わ in かわりました is clearly pronounced
• The り is a light Japanese r sound, not a strong English r

If you are focusing on rhythm, try saying it in chunks:

じたい が / かわりました

Yes, depending on the nuance you want.

Some common alternatives:

• 状況が変わりました。

  • The situation/circumstances changed.
  • More general and common.

• 事情が変わりました。

  • The circumstances have changed.
  • Often used when background conditions or reasons have changed.

• 様子が変わりました。

  • The appearance/state/manner changed.
  • More about how something seems or looks.

But 事態が変わりました is especially good when talking about a significant development in events.