都是连词,意思不同 and 是并列关系,例如 I like apple and banana. but代表转折关系,例如 I like many kinds of fruits,but I do not like apple. so代表顺承关系,例如 The weather looks bad,so we had better take umbrellas. because代表原因,例如 I am very tired,because I have not slept for two days.
