// TRADING TERMINOLOGY
What is Index / Indices?
A market index measures the combined performance of a defined group of stocks, such as the FTSE 100 (the 100 largest UK-listed companies) or the S&P 500.
In-Depth Explanation
Read the full guide: [What Are Indices?](/basic/what-are-indices)
Practical Example
"A trader goes long on the FTSE 100 index via a CFD, profiting when the constituent companies's share prices rise."
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