Mission—Team—FAQ—Privacy—Terms—Sponsors—Grammar—Typing Course—Donate

© 2026 Elon Automation B.V.

Learn Hardcore Japanese: kikai no naibu wo kakuninsita. - I checked the inside of the machine.

Hardcore Japanese
/Hosting a board-game night with friends
/kikai no naibu o kakuninshita.

kikai no naibu o kakuninshita.

Word

機械きかい　の　内部ないぶ　を　確認かくにんした。kikai no naibu o kakuninshita.

Meaning

I checked the inside of the machine.

Part of speech

sentence

Pronunciation

Course

Hardcore Japanese

Lesson

Hosting a board-game night with friends

Breakdown of kikai no naibu o kakuninshita.

direct object particle

possessive case particle

確認かくにんするkakuninsuru

機械きかいkikai

Questions & Answers about kikai no naibu o kakuninshita.

Why is there a の between 機械 and 内部?

の connects two nouns and shows that the second noun belongs to, relates to, or is part of the first.

So:

機械 = machine
内部 = interior / inside
機械の内部 = the inside of the machine / the machine's interior

This is a very common pattern in Japanese:

車のドア = the car's door
家の中 = the inside of the house
学校の先生 = the school's teacher / teacher at the school

In this sentence, 機械の内部 is one noun phrase.

What exactly does 内部 mean here?

内部 means interior, inside, or internal part.

It sounds a bit more formal or technical than everyday words like 中.

Compare:

中（なか） = inside, interior, middle
- more common in everyday speech
内部（ないぶ） = internal area, interior, inside
- more formal, technical, or precise

So 機械の内部 sounds natural for talking about a machine, device, system, or structure.

Why is を used after 内部?

Nihon-shiki romanizationwatasi ha tyuugoku kara kimasita

Hepburn romanizationwatashi wa chuugoku kara kimashita

内部ないぶnaibu

the inside; interior

Elon.io is an online learning platform

We have hundreds of Japanese lessons and thousands of exercises.

Start learning Japanese

Start learning Japanese now

を marks the direct object of the verb.

The verb here is 確認した (confirmed / checked / inspected), and what was checked is 機械の内部.

So:

機械の内部を = the inside of the machine (as the thing being checked)
確認した = checked / confirmed

Even though English often says checked inside the machine, Japanese treats the inside of the machine as the thing directly checked, so を is natural.

What is 確認した grammatically?

確認した is the past plain form of 確認する.

Breakdown:

確認 = confirmation / checking
する = to do
確認する = to confirm / to check
確認した = confirmed / checked

This is a very common type of verb in Japanese: a noun + する.

Other examples:

勉強する = to study
連絡する = to contact
予約する = to reserve
確認する = to confirm/check

Why does the sentence end with した instead of しました?

した is the plain past form, while しました is the polite past form.

So:

確認した。 = checked / confirmed.
- plain style
確認しました。 = checked / confirmed.
- polite style

The sentence you were given is in plain style, which is common in:

written notes
reports
casual narration
textbooks
dictionary-style example sentences

It is not rude by itself; it just has a less formal tone than しました.

Why is there no subject in the sentence?

Japanese often leaves out the subject when it is clear from context.

So 機械の内部を確認した。 could mean:

I checked the inside of the machine.
We checked the inside of the machine.
He/She/They checked the inside of the machine.

Japanese does this very often. If the speaker, topic, or actor is already understood, it does not need to be stated.

If you wanted to include the subject, you could say:

私が機械の内部を確認した。 = I checked the inside of the machine.
彼が機械の内部を確認した。 = He checked the inside of the machine.

But in many situations, leaving it out sounds more natural.

Is 機械の内部 one chunk, or should I think of 内部を確認した as a separate pattern?

It is helpful to think of the sentence in chunks:

機械の内部 = the inside of the machine
機械の内部を = the inside of the machine + object marker
機械の内部を確認した = checked the inside of the machine

So yes, 機械の内部 is one noun phrase, and then を確認した tells you what happened to it.

This is a very useful reading strategy in Japanese: find the noun phrase first, then attach the particle and verb.

How is 確認する different from verbs like 見る, 調べる, or 点検する?

They can all be translated as something like check depending on context, but the nuance is different.

見る = to see / to look at
- very broad and general
調べる = to investigate / examine / look into
- often implies researching or examining in detail
点検する = to inspect / do a safety or maintenance check
- often used for equipment, machinery, systems
確認する = to confirm / verify / check
- often means making sure something is correct, present, or in the expected condition

So 機械の内部を確認した suggests something like:

checked the inside of the machine
confirmed the condition of the machine's interior
made sure everything inside the machine was okay

If the sentence were 機械の内部を点検した, it would sound more like a formal inspection.

Could 内部 be replaced with 中?

Yes, you could say 機械の中を確認した, and it would still be understandable.

However, there is a nuance difference:

機械の中 = inside the machine
- more everyday and direct
機械の内部 = the machine's interior / internal area
- more formal, technical, or report-like

For machinery, manuals, technical explanations, or formal descriptions, 内部 often sounds more natural.

Why are there spaces between the words?

The spaces are almost certainly there for learners.

Normal Japanese writing would usually be:

機械の内部を確認した。

Japanese does not normally put spaces between words the way English does. Educational materials sometimes add spaces to make the structure easier to see.

Does 機械 mean a specific machine here, or machines in general?

By itself, 機械 does not clearly mark singular vs. plural.

So depending on context, it could refer to:

the machine
a machine
sometimes even machines, though singular is more likely here

Japanese usually relies on context rather than articles like a or the.

So in a real situation, the listener would know whether it means:

a particular machine already being discussed
a machine in general
one machine in a work report

What word order is this sentence following?

The basic order is:

[object] を [verb]

So here:

機械の内部 = object
を = object marker
確認した = verb

Japanese verbs usually come at the end of the sentence.

A very literal word-for-word order would be:

machine's interior + object marker + checked

Natural English becomes:

I checked the inside of the machine.
The inside of the machine was checked.
depending on context

Is this sentence natural Japanese?

Yes, it is natural and clear.

It sounds especially natural in contexts like:

maintenance reports
repair work
technical writing
inspection logs
narration of a procedure

For example, in a work report, 機械の内部を確認した。 sounds very normal: concise, factual, and practical.

Your questions are stored by us to improve Elon.io