Is the S&P a derivative?

Could you please clarify for me whether the S&P, as we commonly know it, qualifies as a derivative instrument? I've heard conflicting opinions about this, and I'm seeking a more definitive answer. Some say that it's merely an index representing a basket of stocks, while others argue that its value is derived from the underlying securities it tracks. I'm curious to know which perspective is more accurate. Thank you for your time and assistance in this matter.