这四个词都有“说”的意思，其用法差异主要在于各自强调的对象、内容不同。
(1) say的意思是“说”、“讲”、“说出”，是及物动词，强调“说”的内容。
不仅可指口头“说”，而且可指书面“说”。
eg: ① He said nothing to me. 他对我什么也没说。
② He said in his letter that he was getting on well with his life. 他在信中说，他生活得很好。
固定搭配：say hello/good bye/sorry to sb. 向某人问候/告别/道歉 say “ yes ” to sb . = agree with sb. 同意某人 say “ no ” to sb. = disagree with sb. 不同意某人
(2) speak表“说”、“讲”，它可以表示任何一种方式的“说话”。
它着重“说话”这一动作本身，而不强调所“说”的内容。它通常为不及物动词，但它也可以作及物动词，后接the language、the truth、a word等，或接表示语言名称的名词。
eg: ①Please speak more slowly and clearly. 请说慢些和清楚些。 ②Who is speaking? 你是谁?(打电话时用语) ③Can you speak Japanese? 你会讲日语吗? 固定搭配：speak to sb. 对某人说话 speak highly of 称赞
speak one’s mind 说心里话; 直言不讳
(3) talk表示“交谈”、“谈话”，它指连贯地与人交谈，着重指说话的动作，而不强调说话的内容。它一般用作不及物动词。
eg: ①What are you talking about? 你们在谈论什么? ②We are talking about the Chinese football match. 我们在谈论中国足球比赛。
固定搭配：talk with/to sb. 和某人谈话
talk about sb./sth. 谈论某人/某事
talk with sb. about sth. = talk about sth. with sb.
和某人谈论某事
(4) tell表“告诉”、“讲述”之意，是及物动词，常强调所讲的内容，不表示动作。
重点句式：tell sb. sth = tell sth to sb. 告诉某人某事
eg: He told me nothing. = He told nothing to me. 他什么也没告诉我。
tell sb. (not) to do sth. 告诉某人(不)去做某事 eg: He told us not to worry about him. 他告诉我们不要为他担心。
tell sb. +that-clause/who-clause 告诉某人„„ eg: He told me that he was coming. 他告诉我说他要来。 固定搭配：tell„ from„区分，辨别 tell a story 讲故事