The title of largest valid googologism has belonged to various numbers. For a long period, Rayo's number, which is defined as the smallest number larger than any number expressible in the language of first-order set theory in a googol (\(10^{100}\)) symbols or less, was uncontestedly considered the largest valid googologism; however, it was later upstaged by Fish number 7, but due to some controversy regarding whether it is significantly larger than Rayo's number, it has never been officially recognized as the largest valid googologism, even after it was concluded it's not a naive extension. Fish number 7 adds an oracle formula to the original microlanguage used to define Rayo's number.