kikai ga kyuu ni teisisimasita.

A natural reading is:

きかい が きゅう に ていし しました。

Without the spaces, it would normally be written as:

機械が急に停止しました。

Word-by-word:

• 機械（きかい） = machine
• が = subject marker
• 急に（きゅうに） = suddenly / abruptly
• 停止しました（ていししました） = stopped / came to a stop

が marks 機械 as the grammatical subject of the sentence.

So 機械が means something like the machine is the thing that did the stopping.

In this sentence, が is very natural because it simply identifies what stopped:

• 機械が急に停止しました。 = The machine suddenly stopped.

If you used は instead, the nuance would change:

• 機械は急に停止しました。

That sounds more like as for the machine, it suddenly stopped, which could be fine in the right context, especially if you are contrasting it with something else or talking about the machine as a topic.

So:

• が = focuses on the subject/event
• は = marks the topic, often with contrast or broader context

急に means suddenly or abruptly.

The base word is 急（きゅう）, which can mean sudden or urgent depending on context. Here it works with に to become an adverb:

• 急 → sudden
• 急に → suddenly

This is a very common pattern:

• 静か（しずか） → quiet
• 静かに → quietly

So in this sentence, 急に modifies the verb phrase 停止しました, telling you how the stopping happened: it happened suddenly.

停止しました is the polite past form.

Breakdown:

• 停止する = to stop / to come to a stop / to shut down
• 停止しました = stopped / came to a stop (polite past)

The plain form would be:

• 停止した

So the difference is mainly politeness:

• 停止した = plain/casual
• 停止しました = polite

In formal situations—reports, announcements, explanations, customer service, workplace language—停止しました is very natural.

Both can relate to stopping, but they are not exactly the same in tone and usage.

• 止まる（とまる） = to stop
• 停止する（ていしする） = to stop / cease operation / come to a halt

止まる is more general and common in everyday speech:

• 電車が止まりました。 = The train stopped.
• 機械が止まりました。 = The machine stopped.

停止する is more formal, technical, and mechanical/system-oriented. It is often used for:

• machines
• equipment
• systems
• operations
• devices
• services

So 機械が急に停止しました。 sounds a bit more technical or report-like than 機械が急に止まりました。

Here, 停止する is being used intransitively, meaning the machine itself stopped.

• 機械が停止しました。 = The machine stopped.

There is also a transitive use, where something stops something else:

• 運転を停止しました。 = (Someone) stopped the operation.
• システムを停止しました。 = (Someone) shut down the system.

So 停止する can behave a bit flexibly depending on what is being described. In your sentence, because 機械が is marked with が, the meaning is clearly the machine stopped.

The basic order is:

機械 が 急に 停止しました。
machine + subject marker + suddenly + stopped

Japanese often puts adverbs like 急に before the verb they modify.

So the structure is:

• subject: 機械が
• adverb: 急に
• verb: 停止しました

This is very normal Japanese word order. Japanese verbs usually come at the end of the sentence.

No. Normal Japanese writing does not usually use spaces between words.

So the standard written sentence is:

機械が急に停止しました。

The spaced version is often only used for learners to make the structure easier to see.

Yes, sometimes, but the position in your sentence is the most natural and standard.

Common placement:

• 機械が急に停止しました。

You may also see:

• 急に機械が停止しました。

This puts a little more emphasis on suddenly at the start, like Suddenly, the machine stopped.

So both are possible, but:

• 機械が急に停止しました。 = neutral and very natural
• 急に機械が停止しました。 = slightly more emphasis on the suddenness

Both can mean suddenly, but they are a little different in feel.

• 急に（きゅうに） = suddenly, abruptly; very common and practical
• 突然（とつぜん） = suddenly, all of a sudden; often a bit more dramatic or literary

Examples:

• 機械が急に停止しました。 = The machine suddenly stopped.
• 機械が突然停止しました。 = The machine suddenly stopped.

Both are possible, but 急に often feels more matter-of-fact here, while 突然 can sound a bit stronger or more dramatic.

Yes, it is natural, especially in a formal, technical, or workplace context.

It sounds like something you might hear in:

• a maintenance report
• a factory setting
• an incident description
• a troubleshooting explanation
• an announcement about equipment

If you wanted a more everyday, less technical version, you might say:

• 機械が急に止まりました。

But your original sentence is absolutely natural.

Not as written.

機械が急に停止しました。 means the machine stopped.

If you want to say that someone stopped the machine, you would usually mark machine with を, not が:

• 機械を停止しました。 = (Someone) stopped the machine / shut down the machine.

So the particle helps show the difference:

• 機械が停止しました。 = The machine stopped.
• 機械を停止しました。 = Someone stopped the machine.

Because 停止する is a suru-verb.

Many Japanese nouns can combine with する to make a verb:

• 勉強する = to study
• 運転する = to drive
• 停止する = to stop / shut down / come to a halt

So:

• 停止 = stoppage / halt
• 停止する = to stop
• 停止しました = stopped (polite past)

This is why you see 停止 + しました rather than a single native Japanese verb form.

Yes, depending on context.

Because 停止する is somewhat technical, translations like these can all work:

• The machine suddenly stopped.
• The machine abruptly stopped.
• The machine suddenly shut down.
• The machine came to a sudden halt.

The best English choice depends on what kind of machine it is:

• for a general machine: stopped
• for software/electronics/systems: shut down
• for formal reporting: ceased operation or came to a halt

So if the meaning has already been provided to the learner, it is still useful to know that the Japanese can sound slightly more technical than a simple everyday stopped.