Is a siren a different name for a mermaid?

No, a Siren is a mythical bird-woman from Greek mythology, they sing a mesmerizing song that hypnotizes sailors so they meet there doom. A mermaid is a woman with the upper body of a human, and a fish, eel, dolphin or snake tail, and they were a part of almost every country's myths and tales, they even date back to the Stone Age!

J I hope this helped.