#226 Yamada: magsabi - to speak
Say: Focuses on the content of what's being expressed, often more casual. Example: "I'll say it again."
Speak: More formal, emphasizes the act of vocalizing words, can imply a level of authority. Example: "She spoke at the conference."
Talk: Suggests a more conversational, interactive exchange. Example: "Let's talk about the plan."
In short, "say" is about the words, "speak" is about the act, and "talk" is about the interaction.