1.speak-说,讲,演讲.重点指说的能力及动作,一般为不及物动词.作及物动词时,宾语常是表示语言的词.
Do you speak Chinese?
Mr.Li is going to speak at ourclassmeeting.
2.talk-讲,说话,谈话,指连续不断的说话.与speak意义相近,一用作不及物动词,指一般的谈话或交谈,而不如speak正规的演讲、发言,如需跟宾语时,与to、with、about等介词连用.
Our teacher istalking to（with） the parents.
3.say-一般着重指讲话的内容,指有连贯性的说话,通常用作及物动词.
I don't know what he said.
4.tell-指把一件事情传达给别人或讲述一件事情、一个故事等.常用作及物动词.
常用词组有tell sb (about) sth
tell sb to do sth.
He will tell the good news to everybody in our class.