Write the Word or Phrase That Best Completes Each Statement $x$

Short Answer

Write the word or phrase that best completes each statement or answers the question.
Provide the missing information.
-Given positive real numbers $x$ and $b$ such that $b \neq 1 , y = \log _ { b } x$ is the ـــــــــــــ function base $b$ and is equivalent to $b ^ { y } = x$ .