It was late, so I went home おそかったので いえに かえりました

Four little words let you join two ideas into one sentence. "and" ADDS a similar idea: "I like tea and coffee", "She reads and writes". "but" shows a CONTRAST: "I like tea but not coffee", "It is small but comfortable". "or" gives a CHOICE: "Tea or coffee?", "We can walk or take the bus". "so" shows a RESULT — it goes between the cause and the result: "It was late, so I went home" (cause + so + result). "because" gives a REASON — it goes before the reason: "I went home because it was late" (result + because + cause). So "so" and "because" describe the SAME situation from opposite ends: you can say "I was tired, so I slept" OR "I slept because I was tired", and the order of cause and result flips. Two rules: (1) use only ONE connector per link — do not use "because" and "so" together; (2) in writing, we usually put a comma before "but" and "so" when they join two full sentences. Note: many learners mark both the cause and the result at once, copying their first language: "Because I was tired, so I slept" ✗. Keep just one: "I slept because I was tired" ✓ or "I was tired, so I slept" ✓.

よっつの ちいさな ことばで ふたつの かんがえを ひとつの ぶんに つなげる。"and" は にた かんがえを たす: "I like tea and coffee"、"She reads and writes"。"but" は たいひを しめす: "I like tea but not coffee"、"It is small but comfortable"。"or" は せんたくを あたえる: "Tea or coffee?"、"We can walk or take the bus"。"so" は けっかを しめす — げんいんと けっかの あいだに くる: "It was late, so I went home"（げんいん + so + けっか）。"because" は りゆうを あたえる — りゆうの まえに くる: "I went home because it was late"（けっか + because + げんいん）。だから "so" と "because" は おなじ じょうきょうを りょうたんから えがく: "I was tired, so I slept" とも "I slept because I was tired" とも いえて、げんいんと けっかの じゅんが ぎゃくに なる。ふたつの ルール: (1) ひとつの つなぎに せつぞくしは ひとつ — "because" と "so" を いっしょに つかわない；(2) かくとき、"but" と "so" が かんぜんな ふたつの ぶんを つなぐ ときは ふつう まえに カンマを いれる。ちゅうい: おおくの がくしゅうしゃは ぼこくごを まねて げんいんと けっかを どうじに マークする: "Because I was tired, so I slept" ✗。ひとつだけ のこす: "I slept because I was tired" ✓ か "I was tired, so I slept" ✓。