Say 一般作及物动词用,着重说话的内容,它的宾语可以是名词,代词或宾语从句.
例：He can say his name.他会说他的名字.
She`s saying ,Don`t draw on the wall.她在说“别在墙上画”.
Speak 强调说的动作,不强调所说的内容.作及物动词时,常以某种语言作宾语.作不及物动词时,常见的搭配形式有：speak of something/somebody谈到某事（某人）；speak to sb 跟某人讲话.此外,speak还可用于在较为正式的场合了表演讲或演说.
例：Can you speak Japanese?你会说日语吗?
She is speaking to her teacher.她正在跟她的老师说话.
Talk 一般为不及物动词,意思是“交谈,谈话”,着重强调两者之间的相互说话.
例：She is talking with Lucy in English.她正在和露茜用英语交谈.
What are you talking about?你们在谈论什么?
Tell 常作及物动词,意为“讲述,告诉,动词常跟双宾语.
tell sb sth＝tell sth to sb告诉某人某事.
例：He is telling the children a story.他正在给孩子们讲一个故事.
Did you tell her the news?＝Did you tell the news to her?
你把这个消息告诉她了吗?