Compound Sentence

How to Express Reasons: …から and …ので

Because: から

Last time, you learned how to express time clauses, e.g. “大学生だいがくせいのとき、オーストラリアを旅行りょこうしました (When I was a university student, I traveled to Australia).” Time clauses allow you to more precisely express when actions and events take place. Then, if you would like to say, “I traveled to Australia because my brother lived there” what should you say? In this lesson, you will learn how to express reasons.

Explanation for Usages of …から and …ので

Table of Contents
Difference between から and ので

There are two main sentence patterns used to express reasons, which are から and ので. Since they have very similar conjugations and functions, you can easily use them in conversation. However, the similarity sometimes confuses learners. Therefore, we will explain the usages in detail while paying attention to the differences.

Reasons: …から and …ので


 たい調ちょうわるい(です)から 今日きょう学校がっこうを(やすむ / やすみます)
Reason Conclusion
As for today, [I] will be absent from school because [I] am under the weather.

The function is to express reasons like “because,” “since,” and “so.” The から part is generally placed at the beginning. The conjugation is simple. You can directly attach から to any part of speech, which includes the polite form. As for nouns and na-adjectives, don’t forget to keep the state-of-being style, i.e. to add だ like 元気から.

いまほんなつ(だ / です)から、とてもあつい(です)よ。
[It’s] very hot because [it’s] summer in Japan now.
ほんさかな美味おいしい(です)から、おすすめ(だ / です)よ。
Japanese fishes are delicious, so [they are my] recommendations.
ゆきが(った / りました)から運転うんてんしないほうがいい(です)よ。
[You] shouldn’t drive because [it] snowed.

When you request or invite, reasons can be like conditions or arrangements.

まつりがあるから一緒いっしょに(かない / きませんか)?
There is a festival. Won’t [you] go with me?
This bread is delicious, so please try to eat [it].

As you know, the Japanese language really likes omissions. Surprisingly, even the conclusion part can be omitted when contexts are clear. Actually, you can omit it even if contexts are unclear. This is a kind of technique in conversation. By letting listeners imagine conclusions, you can tell more of what you want to say when compared with not omitting it.

ひどいじゅうたいだね。 => まつりがあるから
[It] is a terrible traffic jam. => Because there is a festival.
[I] am waiting. *She expects listeners to do something for her.


たい調ちょうわるい(です)ので 今日きょうごとを(やすむ / やすみます)
Reason Conclusion
As for today, [I] will be absent from work because [I] am under the weather.

The function is almost the same as から. The difference is that you add な instead of だ when you use nouns and na-adjectives like 元気ので. ので sound a little more formal than から and is preferred in business situations.

明日あしたやすみ(な / です)のでいえべんきょう(する / します)。
Tomorrow is a day off, so [I] will study at home.
タクシーはたかい(です)のでれ(ない / ません)。
[I] cannot take a taxi because [it’s] expensive.
つくえを(はこぶ / はこびます)のでつだってもらえ(る / ますか)?
[I] will carry the desk. Can/could [you] help [me]?
よるあぶない(です)のでそとてはいけ(ない / ません)。
[You] must not go out because [it’s] dangerous at night.
はんべないの? => うん、たい調ちょうわるので
Won’t [you] eat a meal? => No, because [I’m] under the weather.

の will become ん when you speak casually. However, in author’s opinion, this sounds a little masculine and is not recommended if you are female.

明日あしたやすみ(な / です)んでいえべんきょう(する / します)。
タクシーはたかい(です)んでれ(ない / ません)。
つくえを(はこぶ / はこびます)んでつだってもらえ(る / ますか)?
よるあぶない(です)んでそとてはいけ(ない / ません)。
はんべないの? => うん、たい調ちょうわるんで


Difference between から and ので

1. You Can Only Use から with だろう
あめるだろうからはやいえに(かえろう / かえりましょう)。
[It] will probably rain, so let’s go home early.
雨が降るだろうので、早く家に(帰ろう / 帰りましょう)

When you use だろう and the polite form: でしょう which give a nuance of “probably,” you can only use から.

2. Only から Has a Special Sentence Pattern: …のは…からだ
やす  たい調ちょう わるから(だ / です)
Reason Subject Predicate: Reason
[The reason why I will] be absent is that [I’m] under the weather.

This is a sentence pattern to emphasize something. The の of のは comes from the particle の, which functions as a replacement noun. The original sentence should be やすゆうは. With this sentence pattern, you can only use から. For reference, you can utilize this for other topics to emphasize something. Sentences don’t have to end with から if other things are replaced with の.

わたしほんくのは富士ふじさんがあるから(だ / です)。
The reason why I will go to Japan is that there is Mt. Fuji.
わたしべたいのは寿司すし(だ / です)。
The foods which I want to eat is sushi.
わたしきたいのはきょう(だ / です)。
The place where I want to go is Kyoto.

If we don’t use the のは sentence pattern, the above example would be like this:

わたしほんゆう富士ふじさんがあるから(だ / です)。
わたしべたいもの寿司すし(だ / です)。
わたしきたいしょきょう(だ / です)。
3. You Can Ask Reasons by Only Using から
そとあぶないからいえにいないといけない(の / んですか)?
Do [I] have to stay at home because [it’s] dangerous outside?
外が危ないので、家にいないといけない(の / んですか)

When questions practically indicate reasons, you have to use から.

そとあぶないからいえにいないといけないん(だ / です)。
[You] have to stay at home because [it’s] dangerous outside.
外が危ないので、家にいないといけないん(だ / です)。

Similarly, when you respond to such questions, から is more suitable. The above is a response to a question which asks something like “Why do I have to stay at home?”


  1. When you use nouns and na-adjectives, you need だ for から and な for ので.
  2. から and ので can be used with the polite form.
  3. ので sound a little more formal than から.
  4. You can only use から with だろう and でしょう.
  5. When sentences particularly indicate reasons, から is more suitable.

Please keep in mind that it’s kind of rare to see people connect the polite form with these sentence patterns. Generally, Japanese expresses politeness by the end of sentences. Thus, by using the polite form in the middle, it may look very polite and be more suitable for formal situations than everyday life. Next, you will learn a similar expression: how to express aims.

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