The Oxford Learner's Dictionaries are an excellent resource for English learners. https://www.oxfordlearnersdictionaries.com speak - verb https://www.oxfordlearnersdictionaries.com/definition/english/speak_1?q=speak synonyms [excerpt] talk or speak? Speak can suggest a more formal level of communication than talk. You speak to somebody about something to try to achieve a particular goal or to tell them to do something. You talk to somebody in order to be friendly or to ask their advice:

Speak has to do with "utterance" and talk has to do with "conversation."