# What is “oracle” in statistics?

When I read several statistical papers, they mention "oracle" property or "oracle" estimator. What do they mean by "oracle"? I understand this oracle is not a company name, but have no idea what this means.

For example, Candes and Tao 2007 is about "oracle" inequality in a context of large dimensional estimation of linear model (p>>n). https://projecteuclid.org/euclid.aos/1201012958)

Zou 2006 discusses "oracle" property of Lasso. (http://www.tandfonline.com/doi/abs/10.1198/016214506000000735)

I am not familiar with this field but I have to read one paper which discusses high dimensional test in statistics.

• "Even though $n$ may be much smaller than $p$, our estimator achieves a loss within a logarithmic factor of the ideal mean squared error one would achieve with an oracle which would supply perfect information about which coordinates are nonzero, and which were above the noise level.