Expressions of Reason and Cause

Pattern 〜ので・〜から (reason)

The patterns 「〜ので」 and 「〜から」 both express cause or reason and mean 'because'. The part preceded by this pattern is the cause, while the part that follows is the result or the action taken because of that cause. 「〜ので」 sounds more objective and polite, so it is often used in writing or formal situations, whereas 「〜から」 is more direct and emphasizes the reason from the speaker's point of view.

The form used before 「ので」 is the plain form (dictionary form, ない form, or た form). Example: 「風が強いので、洗濯物を中に入れました」 (because the wind was strong, I brought the laundry inside). A dictionary form such as 「降る」(ふる, to fall) is directly followed by 「ので」.

• 〜ので — because (objective and natural reason). Example: 「熱があるので、今日は休みます」 (because I have a fever, I am taking the day off today). The relationship between being sick, for example with 「風邪(かぜ, flu)」, and not going to school or work is a natural cause-and-effect relationship, so 「ので」 is used.
• An い-adjective is directly followed by 「ので」, for example 「寒いので」 (because it is cold). This pattern expresses a reason that triggers the next action.
• An adjective in the past tense or appearance form can also be followed by 「ので」, for example 「おいしそうだったので」 (because it looked delicious).
• Transportation disruptions such as a train stopping can cause delays, and this relationship is expressed with 「ので」.
• In sentence-ordering questions, 「ので」 is placed directly after the plain form of the predicate, and the main predicate of the sentence is placed at the end.
• The 「〜てから」 form (after doing …) indicates the order of events, not a reason. The 「から」 attached to the て form must be distinguished from 「から」 meaning 'because'.
• 「ので」 suits logical and natural reasons, for example there is an exam tomorrow, so I go to bed early today.
• A cause can also be expressed with the て form, such as 「忘れて」 (forgetting), which produces a result in the form of difficulty. This form does not use 「ので」, but it still shows a cause-and-effect relationship.
• In reading passages, 'why' questions usually point to a sentence that uses 「ので」 or 「から」. The correct answer choice is the reason stated directly as the cause, not another reason that is merely mentioned as background.

Pattern 〜ために・〜ように (purpose)

The pattern 「〜ために」 expresses the purpose of an action done deliberately, so it means 'in order to' or 'so that'. This pattern is attached after the dictionary form of a verb (辞書形, じしょけい), for example 「勉強するために」 (in order to study). Because the action is deliberate, the main part of the sentence usually contains a volitional verb or an action verb, such as 「留学したい」 (want to study abroad) or 「行く」(いく, to go).

• 〜ために — in order to (a deliberate purpose). Example: 「試験に合格するために、毎日単語を覚えます」 (in order to pass the exam, I memorize vocabulary every day).
• In sentence structure, 「ために」 is placed after the dictionary form of a verb, while the main predicate of the sentence comes at the end. Example: 「体力をつけるために、毎朝走ります」.
• If the choices offer 「ので」 (because) or 「とき」 (when) to express purpose, both are incorrect because they do not express the intended goal to be achieved.
• 「〜ために」 matches the speaker's own wishes or volition. Meanwhile, 「〜ように」 is used for purpose with a potential verb (can do) or a negative verb, for example 「忘れないように」 (so that one does not forget).
• The pattern 「〜ようになる」 expresses a change in state from not being able to being able, or from not yet to already. Example: 「自転車に乗れるようになった」 (I finally became able to ride a bicycle). This pattern does not express purpose.