Learn Hardcore Japanese: tukue no mannnaka ni memotyou wo okimasu. - I put the notepad in the middle of the desk.

Overall sense: “(I) will put a memo pad in the middle of the desk.”
The subject “I” is omitted, which is normal in Japanese if it’s clear from context.

Why is の used between 机 and 真ん中?

の here works like “of” in English:

机の真ん中 literally = “the middle of the desk”

So:

机の真ん中 = “the desk’s middle” / “the middle of the desk”

This pattern is very common:

部屋の真ん中 – the middle of the room
道の真ん中 – the middle of the road
公園の真ん中 – the middle of the park

What does 真ん中 mean exactly, and what part of speech is it?

真ん中（まんなか） means “(the) very middle / center”.

It’s a noun, not an adjective.

You can think of it like the English noun “center”:

机の真ん中 – the center of the desk
真ん中に座る – sit in the middle

Because it’s a noun, you often see it with の when it modifies another noun:

真ん中の席 – the middle seat
真ん中のページ – the middle page

Why is the particle に used after 真ん中 instead of で?

に is used here because we’re talking about the destination / final position of placing something.

に after a location can mark:
- a target of movement: where something goes or ends up
- a resulting location: where something will be when the action is finished

So:

机の真ん中にメモ帳を置きます。
= “I will put the memo pad (so that it ends up) in the middle of the desk.”

If you used で:

机の真ん中でメモ帳を置きます。

this would sound like the action of placing happens “in the middle of the desk” (as in doing some activity there), which is odd for 置く. With verbs of putting/placing like 置く, the place where it ends up normally takes に.

What role does を play in メモ帳を置きます?

を marks the direct object of the verb.

メモ帳を置きます。
= “(I) will put the memo pad.”

In this sentence:

メモ帳 is what is being put.
置きます is what is being done to it.
So メモ帳 is the direct object, marked by を.

Pattern:

[thing] を置きます – put [thing]
- 本を置きます – put down a book
- かばんを置きます – put down a bag

Where is the subject (like “I”) in this sentence?

The subject is omitted, which is very common in Japanese.

The full sentence could be:

私は机の真ん中にメモ帳を置きます。
- 私 – I
- は – topic marker

But if it’s already clear from context that you are the one putting it, Japanese naturally drops “I”:

机の真ん中にメモ帳を置きます。
Context decides whether the meaning is “I (will) put…”, “You (will) put…”, “He/She (will) put…”, etc.

What is the dictionary form of 置きます, and what tense or aspect does it have?

The dictionary form is 置く（おく）.

置きます is the polite, non-past form.

Non-past in Japanese covers:

Future / planned actions
- 明日、ここに本を置きます。
  “I will put the book here tomorrow.”
Regular / habitual actions
- いつもここにメモ帳を置きます。
  “I always put the memo pad here.”

Context tells you whether it’s future, present, or habitual.

Can I change the word order? For example: メモ帳を机の真ん中に置きます?

Yes. Japanese word order is relatively flexible as long as the particles stay with their words.

All of these are natural:

机の真ん中にメモ帳を置きます。
メモ帳を机の真ん中に置きます。

Both mean the same thing: “I will put the memo pad in the middle of the desk.”

General rule:

The verb usually comes last.
Everything before that can be rearranged, but the particle must stay attached to its word:
- 机の真ん中に
- メモ帳を

Does 机 mean “desk” or “table”? How is it typically used?

机（つくえ） is usually closer to “desk” in English, especially a work desk:

School desk
Office desk
Study desk

For a general table, Japanese more often uses テーブル:

ダイニングテーブル – dining table
コーヒーテーブル – coffee table

That said, in some contexts, 机 can feel like “table” in English, but the core image is a desk-like piece of furniture you work or study at.

Why is there no word like “on” (as in “on the desk”) in Japanese?

In Japanese, relationships like “on, in, under” are often expressed with nouns + の + location word and the particle に.

Here, 机の真ん中に is understood as:

“in the middle of the desk” (usually the middle of its surface)

If you want to be very explicit about “on (top of) the desk”, you could say:

机の上の真ん中にメモ帳を置きます。
literally: “I will put the memo pad in the middle of the top of the desk.”

But in normal conversation, 机の真ん中に already implies “in the middle of the desk (surface)” unless context suggests otherwise.

What’s the difference between メモ and メモ帳?

メモ – “a memo / note” (the content or the act of jotting something)
メモ帳（メモちょう） – “a memo pad / notepad” (the physical object you write memos in)

In this sentence:

メモ帳を置きます – “(I) will put the memo pad (down).”

If you said:

メモを置きます, it would sound like “I will put (a) memo” (the memo itself), which is less natural in this physical-placing context.

Why is there no particle after 机? It goes straight into 机の真ん中.

机の真ん中 is one noun phrase:

机 – desk
の – of
真ん中 – middle

This whole chunk means “the middle of the desk.”

So the location particle に attaches to the whole phrase:

机の真ん中に
not
机にの真ん中

Structure:

[NOUN1] の [NOUN2] に …
- 机の真ん中に – in the middle of the desk
- 部屋の真ん中に – in the middle of the room
- 道の真ん中に – in the middle of the road

Is 置きます polite, casual, or formal? How would I say this casually?

置きます is polite speech (です／ます style).

Polite:
- 机の真ん中にメモ帳を置きます。

Casual/plain form uses 置く:

机の真ん中にメモ帳を置く。

Both mean the same thing; the choice depends on who you’re talking to:

With friends / family: 置く (casual) is common.
With teachers, customers, or in formal situations: 置きます (polite) is appropriate.