Speak and talk are generally synonyms except when you're referring to the languages you speak. At least in North America, we don't say we talk a language; we say we speak it. For example, "I speak Italian." (Not "I talk Italian"). Tell and say are often synonyms, but tell usually has an indirect object, while say usually has ONLY a direct object. In English, we tell something to someone (i.e., tell Santa what you want for Christmas). We don't tell something. However we to say something (i.e., say what you think). I hope that makes sense. I would be happy to answer any questions in English, French, Italian, or Spanish.