Particles like で, に, を, は are some of the most difficult grammar points for Japanese learners.

Many Japanese learners in upper levels still get confused about how to use particles correctly. But you don't have to be too worried.

The key to understand particles is to grasp the concept of each particle.

Let’s understand the basic concept of で (de) and use it like a native Japanese.

で (de) particle

で (de) is one of the basic Japanese particles and is mainly used for four types of expressions.

The basic concept of the で (de) particle is “a boundary.”

It doesn’t mean that Japanese people are making boundaries in their heads every time they use a で(de) particle. But the boundary image is key to understand the で(de) particle.

The で(de) particle has four usages. One is a place, second is means and use, third is amount, and fourth is time and period. Let’s look at some examples!

場所ばしょ Place

The で(de) particle can be used for describing the place where you do something. The grammar is as follows:

Your action is done within the boundary.

For example, when you want to say “I’ll play at the park with friends,” you say 友達ともだちと公園こうえんで遊あそぶ.

The park is chosen for the place of action and is in the boundary that is separate from other places.

When you say you’ll sleep in a bed, you say ベッドで寝ねる. Your action “sleeping” is done in a bed (boundary).

友達ともだちと公園こうえんで遊あそぶ
Play at the park with friends

ベッドで寝ねる
Sleep in a bed

図書館としょかんで勉強べんきょうする
Study in a library

手段しゅだん・方法ほうほう means and use

The second role of the で(de) particle is to describe means and use. You can specify what you use for the action. When you use the で (de) particle, the grammar is:

For example, when you want to say, “I’ll go to school by bicycle,” you say 自転車じてんしゃで学校がっこうに行いく.

The idea is that the bicycle is in the boundary that separates from other transportations, like the picture as follows.

You can also use this for speaking languages because the language is the means you are using to speak. For example, “I speak in Japanese” is 日本語にほんごで話はなす. The で (de) particle means that you speaking in Japanese and not any other language.

自転車じてんしゃで学校がっこうに行いく
I go to school by bicycle

日本語にほんごで話はなす
I speak in Japanese

包丁ほうちょうで野菜やさいを切きる
I cut vegetables with a knife

個数こすうなどの単位たんい the amount

The で(de) particle can be used when you specify the amount of something. 

For example, there are peaches that cost 500 yen for two of them, you can say この桃ももは2個こで500円えんです. The grammar is as follows:

この桃ももは2個こで500円えんです。
You can buy these two peaches with 500 yen.

4人にんで部屋へやを借かりる
Rent a room with four people.

3人にんで会社かいしゃを始はじめる
Start a company with three people

時間じかん/期間きかん a period of time

The で particle can be used for describing a period of time. For example, you can say summer vacation will end three days later: あと3日かで夏休なつやすみが終おわる.

The boundary partitions a term in time like the picture as follows. The red line is the time of the action.

あと3日かで夏休なつやすみが終おわる
Summer vacation will end in three days.

授業じゅぎょうは５時じで終おわる
The class will end at 5.

Work cited

○いちばんやさしい日本語教育入門 by 今井新悟
Easiest Introductory Japanese Teacher's manual by Shingo Imai, published in 2019