这四个词都有“说话”的意思,就像“一家子”,但毕竟还有区别：
[speak]：只是表示“说”、“说话”,或发出话语的声音,而不管内容是什么.如：
She is speaking to the assistant.
You speak English.
[say]：不仅表明“说”,而且是有内容的,在直接引语或间接引语前后,通常都用say ,如：
He sayshev's goingtohelp me .
“I won't come .”said Tom .
It's hard to say who it was.
[tell]：它的意思是“告诉”,即传达给某人关于别的事情,如：
Thenext dayin school, shetold Tom about the note .
[talk]:意思是“交谈”、“谈论”,一般指相互间的谈话,且没有一定的内容.有时要谈到关于某人某事时,后接介词 about 或 of ,（还可作名词）如：
In the bus we sattogether and talked.
We offen talkabout our work and study.
I had a long talk with her.