watasi ha kuroi boorupen de tetyou ni yotei wo kakimasu.

は marks 私 as the topic of the sentence: as for me, ....

In this sentence, 私は sets up who is doing the action, and the rest of the sentence explains what that person does.

If you used が instead, it would sound more like you are specifically identifying me as the person who writes it, often with more emphasis or contrast.

So here:

• 私は = As for me, ... / I ...
• 私が = I am the one who ... (more focus on I)

For a simple neutral sentence like this, は is very natural.

黒い is an i-adjective, and it directly modifies the noun ボールペン.

So:

• 黒い = black
• ボールペン = ballpoint pen
• 黒いボールペン = a black ballpoint pen

This works just like English adjective + noun order.

A learner may expect 黒のボールペン, and that is also possible in some contexts, but 黒いボールペン is the most straightforward and natural way to say a black ballpoint pen.

で marks the means, tool, or method used to do an action.

Here, the action is 書きます (write), and the tool used is the pen:

• 黒いボールペンで = with a black ballpoint pen

So で answers the question using what?

Common similar examples:

• 箸で食べます = eat with chopsticks
• 日本語で話します = speak in Japanese
• バスで行きます = go by bus

In this sentence, で does not mean location; it means by means of / with.

Here, に marks the place where something is written onto.

So:

• 手帳に書きます = write in a planner/notebook

With verbs like 書く (to write), に often marks the surface or destination of the writing:

• ノートに書く = write in a notebook
• 紙に書く = write on paper
• 黒板に書く = write on the blackboard

Even though English may use in or on, Japanese often uses に for the place where the writing appears.

を marks the direct object of the verb.

The verb is 書きます (write), and the thing being written is 予定 (plans, schedule items, appointments):

• 予定を書く = write plans / write down a schedule

So 予定を tells you what is being written.

A useful pattern is:

• A に B を 書く
• write B in/on A

In this sentence:

• 手帳に = in the planner
• 予定を = the plans/schedule items
• 書きます = write

Yes, both connect to 書く, but they show different roles.

• 手帳に = where the writing goes
• 予定を = what is written

So the structure is:

• [place written to] に
• [thing written] を
• 書きます

This is very common in Japanese. A verb can have more than one related phrase, with each particle showing a different function.

予定 often means plans, schedule, appointments, or things you plan to do.

In a sentence with 手帳, it usually means something like:

• planned events
• appointments
• schedule entries
• things on your calendar

So this is not usually about writing a full abstract life plan. It more naturally suggests writing down planned events or schedule items in a planner.

Japanese normally places the main verb at the end of the sentence.

That means a basic Japanese sentence often builds up information first, and then gives the action last.

Here the order is roughly:

• 私は = as for me
• 黒いボールペンで = with a black ballpoint pen
• 手帳に = in my planner
• 予定を = plans / schedule items
• 書きます = write

This is a standard Japanese sentence pattern, so seeing the verb at the end is completely normal.

The order is somewhat flexible, because the particles show each word’s role.

For example, these are also understandable:

• 私は手帳に黒いボールペンで予定を書きます。
• 私は予定を手帳に黒いボールペンで書きます。

However, not every order sounds equally natural in every context. The original sentence is clear and natural.

A good rule for learners is:

• Particles are what matter most for grammar
• Word order can shift for emphasis, but the verb usually stays at the end

書きます is the polite non-past form of 書く.

It can mean:

• write
• will write
• habitually write

In a simple example sentence, 書きます is often used because it is the basic polite form.

Other forms would change the meaning:

• 書きますか = Do you write...? / Will you write...? (question)
• 書いています = am writing / write regularly depending on context

So 書きます is just the normal polite dictionary-style sentence form for learners.

Yes, Japanese could very often leave 私 out if the subject is already understood from context.

So a natural sentence could simply be:

• 黒いボールペンで手帳に予定を書きます。

That would still be perfectly understandable in many situations.

Japanese often omits subjects when they are obvious. But in textbook sentences, 私 is often included to make the structure easier to follow.

Not exactly.

手帳 usually means a planner, datebook, or personal schedule book. It often suggests something used to keep appointments or plans.

A general notebook is more often:

• ノート = notebook

So:

• 手帳に予定を書く feels very natural because planners are used for schedules
• ノートに予定を書く is possible, but it sounds more like writing plans in a notebook rather than in a planner

No, normal Japanese writing usually does not put spaces between words like this.

Standard writing would look like:

私は黒いボールペンで手帳に予定を書きます。

Spaces are often added in learning materials to help beginners see the parts more clearly.

So the spaced version is just a teaching aid, not standard everyday writing.