1. To speak louder: This is the most common meaning of "speak up". It means to raise your voice so that people can hear you more clearly.
* Example: "Could you please speak up? I can't hear you."
2. To express your opinion or thoughts: This meaning implies being bold and assertive in expressing yourself.
* Example: "I know you're all afraid to speak up, but we need to address this issue."
* Example: "It's important for everyone to speak up and share their ideas."
Here are some other nuances of "speak up":
* To defend yourself or someone else: "I spoke up for my friend when he was being bullied."
* To complain about something: "I'm going to speak up to the manager about the poor service."
The meaning of "speak up" will usually be clear from the context of the sentence.