for是對等連接詞，只能出現在句中，而且只能連接完整句。For之前要加逗點，because是附屬連接詞，可出現於句首，也可出現在句中。 例句： Because Jane was hungry, she ate up the cake.（○） ＝Jane ate up the cake because she was hungry.（○） ＝Jane ate up the cake, for she was hungry.（○） For Jane was hungry, she ate up the cake.（X）
