Estas words have similar meanings, but they are very different:
TALK X SPEAK
TALK se refere a two ou more people having a conversation.
E.g.: We talked about the new project.
SPEAK is used para descrever a ação física de emitir palavras, ou uma one-way communication. Também descreve a person’s ability de speak a language.
E.g. 1: I need to speak to you after class.
E.g. 2: She speaks five languages!
SAY is used para transmitir information, opinions, feelings, instructions ou ainda intention.
E.g. 1: Say no to racism.
E.g. 2: Say your name em voz alta, please.
Gostou deste topic? Access https://www.tolearnenglish.com/exercises/exercise-english-2/exercise-english-87821.php to learn more about it.