A rational expression with a common factor in numerator and denominator is best described as:

1. The definition of simplified sets the test. 2. A rational expression is considered simplified if there are no common factors. 3. That applies to its numerator and denominator. 4. A shared factor means that condition is not met. 5. So the expression is not yet simplified. _Source: OpenStax Elementary Algebra 2e (CC BY 4.0), Ch 8 'Rational Expressions and Equations', sections 8.1-8.9_