The verbs say, speak, talk and tell have to do with the utterance of words or the expression of meaning. They refer to formal or informal vocal exchanges.
Say To say something means to use your voice to produce words: 'I'll always love you,' said Roger.
We can use 'it' after 'said' to refer to the words a person used when they expressed something: Roger said it very romantically.
However, if we are referring to what someone has expressed rather than their actual words, we use 'so', not 'it': 'Actually, I don't like Roger at all, but I didn't say so.' We can also use 'say' and a 'that-clause' to report what someone has said without mentioning their exact words: 'He said that I was beautiful!' 'She said I was too ugly!' We do not use 'say' for the following: 'Doctor Brayne asked me lots of questions about my dreams.' 'The general gave the order to attack.' Also: 'He called me a liar/cheat/traitor/fool, etc...' Speak + Talk When we 'speak', we use our voice to produce words: 'She spoke so quietly that I could not hear what she was saying.' We also say that someone 'speaks' or 'can speak' a foreign language: 'Fred can speak four languages fluently.' If two or more people are having a conversation, we usually say that they are talking (not 'are speaking'): 'Rebecca and Kathy were talking for four hours on the phone last night.' But when we make a telephone call, we ask if we can 'speak' to someone (not 'talk'): 'Hello. Could I speak to Polly, please?' To 'speak to' or 'talk to' someone means to have a conversation with them: 'I always enjoy talking to Agatha.' If you 'speak about' something, you describe it to a group of people (eg, in a lecture): He spoke about his adventures in Central Asia.
But we use 'talking about': (a) in conversation, to refer to the thing someone is discussing: I think I've seen the film you're talking about.
(b) to refer in a general way to what someone is saying: 'What are you talking about?' (c) if two or more people are discussing something: The boys were talking about football.
Tell If someone 'tells' you something, they give you some information. We often refer to this information with a 'that-clause' or a 'wh-clause': 'Please tell me why you're angry.' 'He told me he had a gun, so I gave him all money.' 'Tell' with direct and indirect objects: When the direct object of 'tell' is not a pronoun, you put the indirect object first: I told her the bad news.