To say is to declare or assert.It governs direct objects only.
To speak is to utter words to express thoughts.
To talk is to carry on conversation.
To tell is to uniform or narrate.It governs both direct and indirect objects.
1. He said,"What a man has done a man can do."
2. He said,"What is your name?."
1. He speaks in such a low voice that no one can hear him.
2. He speaks loud.
1. We talked for some time and took leave of each other.
2. He is talking with his girlfriend.
1. He told us all that he knew about the affair.
2. He told us the story in an attractive manner.
3. I told you not to do this.