What types of words require particles in formal Japanese? When are they needed, and when are they not in formal writing?


Sometimes I see sentences and the words are just there, with no particles to
link them, but the verbs are in ます form, which makes me think it is still a
formal sentence. For example: 「私、毎朝１０キロ走っています。」Is this formal? Are some
particles omitted? Often times I see sentences such as this where words like
毎朝, 今日, etc, do not have particles.

So, my question is, what types of words **must** be linked with a particle,
and what words do not in formal Japanese? Or, is it context dependent? Or is
my understanding flawed and the above is not at all formal and all words must
be linked with particles?




It's **word** -dependent. The formal version of that sentence is:

> 私 **は** 毎朝10キロ走っています。

There must be は after 私. There **must not** be any particle after 毎朝. You can
add を after 10キロ, but it's completely optional, and adding it does not make
the sentence sound any more formal.

Many words work both as a noun/adjective and as an adverb. If you look up a
word in a dictionary, you can see its part of speech like this:

![jisho.org](https://i.stack.imgur.com/pbE8j.png)

Since 毎朝 is an adverb, you can use it without any particle.

The number of such words is large, and you basically have to remember them
individually. But there are some tendencies.

  * Time-related words: 毎朝 (every morning), 昨日 (yesterday), 今日 (today), 明日 (tomorrow), 来年 (next year), 昨夜 (last night), 昔 (long time ago), 最近 (recently)
  * [Quantity-related words](https://japanese.stackexchange.com/q/36890/5010): 10キロ, 3つ, 5回, 一部 (part; partly), 全部 (everything)
  * Suffixes such as くらい, 通り, ごろ
  * Others: 偶然, 大抵, 早速

Note that English is equally confusing. There are words that act both as both
a noun and a verb ( _report_ , _drink_ , _increase_ ), words that act both as
an adjective and an adverb ( _fast_ , _early_ , _daily_ ), words that act as a
noun, an adjective and an adverb ( _most_ ), and so on. Learners must look
them up in a dictionary.




It's **word** -dependent. The formal version of that sentence is:

> 私 **は** 毎朝10キロ走っています。

There must be は after 私. There **must not** be any particle after 毎朝. You can
add を after 10キロ, but it's completely optional, and adding it does not make
the sentence sound any more formal.

Many words work both as a noun/adjective and as an adverb. If you look up a
word in a dictionary, you can see its part of speech like this:

![jisho.org](https://i.stack.imgur.com/pbE8j.png)

Since 毎朝 is an adverb, you can use it without any particle.

The number of such words is large, and you basically have to remember them
individually. But there are some tendencies.

  * Time-related words: 毎朝 (every morning), 昨日 (yesterday), 今日 (today), 明日 (tomorrow), 来年 (next year), 昨夜 (last night), 昔 (long time ago), 最近 (recently)
  * [Quantity-related words](https://japanese.stackexchange.com/q/36890/5010): 10キロ, 3つ, 5回, 一部 (part; partly), 全部 (everything)
  * Suffixes such as くらい, 通り, ごろ
  * Others: 偶然, 大抵, 早速

Note that English is equally confusing. There are words that act both as both
a noun and a verb ( _report_ , _drink_ , _increase_ ), words that act both as
an adjective and an adverb ( _fast_ , _early_ , _daily_ ), words that act as a
noun, an adjective and an adverb ( _most_ ), and so on. Learners must look
them up in a dictionary.

